diff --git a/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecFileSyncOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecFileSyncOptions.scala
index a9871efd5..d1dba01f2 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecFileSyncOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecFileSyncOptions.scala
@@ -29,16 +29,16 @@ import scala.scalajs.js.|
   * @param gid        Sets the group identity of the process. (See setgid(2).)
   * @param windowsHide Hide the subprocess console window that would normally be created on Windows systems. Default: `false`.
   */
-class ExecFileSyncOptions(val cwd: js.UndefOr[String] = js.undefined,
-                          val input: js.UndefOr[Input],
-                          val stdio: js.UndefOr[StdIo] = js.undefined,
-                          val env: js.UndefOr[js.Object] = js.undefined,
-                          val encoding: js.UndefOr[String] = js.undefined,
-                          val shell: js.UndefOr[Boolean | String] = js.undefined,
-                          val timeout: js.UndefOr[Int] = js.undefined,
-                          val maxBuffer: js.UndefOr[Int] = js.undefined,
-                          val killSignal: js.UndefOr[KillSignal] = js.undefined,
-                          val uid: js.UndefOr[UID] = js.undefined,
-                          val gid: js.UndefOr[GID] = js.undefined,
-                          val windowsHide: js.UndefOr[Boolean] = js.undefined)
+class ExecFileSyncOptions(var cwd: js.UndefOr[String] = js.undefined,
+                          var input: js.UndefOr[Input] = js.undefined,
+                          var stdio: js.UndefOr[StdIo] = js.undefined,
+                          var env: js.UndefOr[js.Object] = js.undefined,
+                          var encoding: js.UndefOr[String] = js.undefined,
+                          var shell: js.UndefOr[Boolean | String] = js.undefined,
+                          var timeout: js.UndefOr[Int] = js.undefined,
+                          var maxBuffer: js.UndefOr[Int] = js.undefined,
+                          var killSignal: js.UndefOr[KillSignal] = js.undefined,
+                          var uid: js.UndefOr[UID] = js.undefined,
+                          var gid: js.UndefOr[GID] = js.undefined,
+                          var windowsHide: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecOptions.scala
index e5362e847..481e1d7af 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/child_process/ExecOptions.scala
@@ -25,15 +25,15 @@ import scala.scalajs.js.|
   * @param windowsVerbatimArguments No quoting or escaping of arguments is done on Windows.
   *                                 Ignored on Unix. This is set to true automatically when shell is specified and is CMD. Default: false.
   */
-class ExecOptions(val cwd: js.UndefOr[String] = js.undefined,
-                  val env: js.UndefOr[js.Object] = js.undefined,
-                  val encoding: js.UndefOr[String] = js.undefined,
-                  val shell: js.UndefOr[Boolean | String] = js.undefined,
-                  val timeout: js.UndefOr[Int] = js.undefined,
-                  val maxBuffer: js.UndefOr[Int] = js.undefined,
-                  val killSignal: js.UndefOr[KillSignal] = js.undefined,
-                  val uid: js.UndefOr[UID] = js.undefined,
-                  val gid: js.UndefOr[GID] = js.undefined,
-                  val windowsHide: js.UndefOr[Boolean] = js.undefined,
-                  val windowsVerbatimArguments: js.UndefOr[Boolean] = js.undefined)
+class ExecOptions(var cwd: js.UndefOr[String] = js.undefined,
+                  var env: js.UndefOr[js.Object] = js.undefined,
+                  var encoding: js.UndefOr[String] = js.undefined,
+                  var shell: js.UndefOr[Boolean | String] = js.undefined,
+                  var timeout: js.UndefOr[Int] = js.undefined,
+                  var maxBuffer: js.UndefOr[Int] = js.undefined,
+                  var killSignal: js.UndefOr[KillSignal] = js.undefined,
+                  var uid: js.UndefOr[UID] = js.undefined,
+                  var gid: js.UndefOr[GID] = js.undefined,
+                  var windowsHide: js.UndefOr[Boolean] = js.undefined,
+                  var windowsVerbatimArguments: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/child_process/ForkOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/child_process/ForkOptions.scala
index 6737c2152..830bb675c 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/child_process/ForkOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/child_process/ForkOptions.scala
@@ -21,13 +21,13 @@ import scala.scalajs.js.|
   * @param uid      Sets the user identity of the process. (See setuid(2).)
   * @param gid      Sets the group identity of the process. (See setgid(2).)
   */
-class ForkOptions(val cwd: js.UndefOr[String] = js.undefined,
-                  val detached: js.UndefOr[Boolean] = js.undefined,
-                  val env: js.UndefOr[js.Object] = js.undefined,
-                  val execPath: js.UndefOr[String] = js.undefined,
-                  val execArgv: js.UndefOr[Array[String]] = js.undefined,
-                  val silent: js.UndefOr[Boolean] = js.undefined,
-                  val stdio: js.UndefOr[String | Array[String]] = js.undefined,
-                  val uid: js.UndefOr[UID] = js.undefined,
-                  val gid: js.UndefOr[GID] = js.undefined)
+class ForkOptions(var cwd: js.UndefOr[String] = js.undefined,
+                  var detached: js.UndefOr[Boolean] = js.undefined,
+                  var env: js.UndefOr[js.Object] = js.undefined,
+                  var execPath: js.UndefOr[String] = js.undefined,
+                  var execArgv: js.UndefOr[Array[String]] = js.undefined,
+                  var silent: js.UndefOr[Boolean] = js.undefined,
+                  var stdio: js.UndefOr[String | Array[String]] = js.undefined,
+                  var uid: js.UndefOr[UID] = js.undefined,
+                  var gid: js.UndefOr[GID] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/child_process/SendOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/child_process/SendOptions.scala
index ff7ef2e2e..b0fe29a81 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/child_process/SendOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/child_process/SendOptions.scala
@@ -3,5 +3,5 @@ package io.scalajs.nodejs.child_process
 import scala.scalajs.js
 
 class SendOptions(
-    val keepOpen: js.UndefOr[Boolean] = js.undefined
+    var keepOpen: js.UndefOr[Boolean] = js.undefined
 ) extends js.Object {}
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnOptions.scala
index ec2c40515..c2a272677 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnOptions.scala
@@ -20,14 +20,14 @@ import scala.scalajs.js.|
   *                 The shell should understand the -c switch on UNIX, or /d /s /c on Windows. Defaults to false (no shell).
   */
 class SpawnOptions(
-    val cwd: js.UndefOr[String] = js.undefined,
-    val env: js.Any = js.undefined,
-    val argv0: js.UndefOr[String] = js.undefined,
-    val stdio: js.UndefOr[StdIo] = js.undefined,
-    val detached: js.UndefOr[Boolean] = js.undefined,
-    val uid: js.UndefOr[Int] = js.undefined,
-    val gid: js.UndefOr[Int] = js.undefined,
-    val shell: js.UndefOr[Boolean | String] = js.undefined,
-    val windowsVerbatimArguments: js.UndefOr[Boolean] = js.undefined,
-    val windowsHide: js.UndefOr[Boolean] = js.undefined
+    var cwd: js.UndefOr[String] = js.undefined,
+    var env: js.Any = js.undefined,
+    var argv0: js.UndefOr[String] = js.undefined,
+    var stdio: js.UndefOr[StdIo] = js.undefined,
+    var detached: js.UndefOr[Boolean] = js.undefined,
+    var uid: js.UndefOr[Int] = js.undefined,
+    var gid: js.UndefOr[Int] = js.undefined,
+    var shell: js.UndefOr[Boolean | String] = js.undefined,
+    var windowsVerbatimArguments: js.UndefOr[Boolean] = js.undefined,
+    var windowsHide: js.UndefOr[Boolean] = js.undefined
 ) extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnSyncOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnSyncOptions.scala
index c132e9249..88dfe3882 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnSyncOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/child_process/SpawnSyncOptions.scala
@@ -33,18 +33,18 @@ import scala.scalajs.js.|
   * @param windowsVerbatimArguments No quoting or escaping of arguments is done on Windows.
   *                                 Ignored on Unix. This is set to true automatically when shell is specified and is CMD. Default: false.
   */
-class SpawnSyncOptions(val cwd: js.UndefOr[String] = js.undefined,
-                       val input: js.UndefOr[Input] = js.undefined,
-                       val argv0: js.UndefOr[String] = js.undefined,
-                       val stdio: js.UndefOr[StdIo] = js.undefined,
-                       val env: js.UndefOr[js.Object] = js.undefined,
-                       val encoding: js.UndefOr[String] = js.undefined,
-                       val shell: js.UndefOr[Boolean | String] = js.undefined,
-                       val timeout: js.UndefOr[Int] = js.undefined,
-                       val maxBuffer: js.UndefOr[Int] = js.undefined,
-                       val killSignal: js.UndefOr[KillSignal] = js.undefined,
-                       val uid: js.UndefOr[UID] = js.undefined,
-                       val gid: js.UndefOr[GID] = js.undefined,
-                       val windowsHide: js.UndefOr[Boolean] = js.undefined,
-                       val windowsVerbatimArguments: js.UndefOr[Boolean] = js.undefined)
+class SpawnSyncOptions(var cwd: js.UndefOr[String] = js.undefined,
+                       var input: js.UndefOr[Input] = js.undefined,
+                       var argv0: js.UndefOr[String] = js.undefined,
+                       var stdio: js.UndefOr[StdIo] = js.undefined,
+                       var env: js.UndefOr[js.Object] = js.undefined,
+                       var encoding: js.UndefOr[String] = js.undefined,
+                       var shell: js.UndefOr[Boolean | String] = js.undefined,
+                       var timeout: js.UndefOr[Int] = js.undefined,
+                       var maxBuffer: js.UndefOr[Int] = js.undefined,
+                       var killSignal: js.UndefOr[KillSignal] = js.undefined,
+                       var uid: js.UndefOr[UID] = js.undefined,
+                       var gid: js.UndefOr[GID] = js.undefined,
+                       var windowsHide: js.UndefOr[Boolean] = js.undefined,
+                       var windowsVerbatimArguments: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/crypto/Cipher.scala b/app/current/src/main/scala/io/scalajs/nodejs/crypto/Cipher.scala
index 3139da855..b7c46a83a 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/crypto/Cipher.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/crypto/Cipher.scala
@@ -86,7 +86,7 @@ sealed trait Cipher extends Transform {
 
 }
 
-class SetAADOptions(override val transform: js.UndefOr[js.Function] = js.undefined,
-                    override val flush: js.UndefOr[js.Function] = js.undefined,
-                    val plaintextLength: js.UndefOr[Int] = js.undefined)
+class SetAADOptions(transform: js.UndefOr[js.Function] = js.undefined,
+                    flush: js.UndefOr[js.Function] = js.undefined,
+                    var plaintextLength: js.UndefOr[Int] = js.undefined)
     extends TransformOptions(transform, flush) {}
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/crypto/Crypto.scala b/app/current/src/main/scala/io/scalajs/nodejs/crypto/Crypto.scala
index a6e9bb115..413abc91d 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/crypto/Crypto.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/crypto/Crypto.scala
@@ -390,34 +390,34 @@ object Constants extends js.Object {
 
 class CreatePrivateKeyOptions(
     val key: String | Buffer,
-    val format: js.UndefOr[String] = js.undefined,
-    val `type`: js.UndefOr[String] = js.undefined,
-    val passphrase: js.UndefOr[String | Buffer] = js.undefined
+    var format: js.UndefOr[String] = js.undefined,
+    var `type`: js.UndefOr[String] = js.undefined,
+    var passphrase: js.UndefOr[String | Buffer] = js.undefined
 ) extends js.Object
 
 class CreatePublicKeyOptions(
     val key: String | Buffer,
-    val format: js.UndefOr[String] = js.undefined,
-    val `type`: js.UndefOr[String] = js.undefined
+    var format: js.UndefOr[String] = js.undefined,
+    var `type`: js.UndefOr[String] = js.undefined
 ) extends js.Object
 
 class GenerateKeyPairOptions(
     val modulusLength: Int,
-    val publicExponent: js.UndefOr[Int] = js.undefined,
-    val divisorLength: js.UndefOr[Int] = js.undefined,
-    val namedCurve: js.UndefOr[String] = js.undefined,
-    val publicKeyEncoding: js.UndefOr[KeyObjectExportOptions] = js.undefined,
-    val privateKeyEncoding: js.UndefOr[KeyObjectExportOptions] = js.undefined
+    var publicExponent: js.UndefOr[Int] = js.undefined,
+    var divisorLength: js.UndefOr[Int] = js.undefined,
+    var namedCurve: js.UndefOr[String] = js.undefined,
+    var publicKeyEncoding: js.UndefOr[KeyObjectExportOptions] = js.undefined,
+    var privateKeyEncoding: js.UndefOr[KeyObjectExportOptions] = js.undefined
 ) extends js.Object
 
 class ScryptOptions(
-    val cost: js.UndefOr[Int] = js.undefined,
-    val blockSize: js.UndefOr[Int] = js.undefined,
-    val parallelization: js.UndefOr[Int] = js.undefined,
-    val N: js.UndefOr[Int] = js.undefined,
-    val r: js.UndefOr[Int] = js.undefined,
-    val p: js.UndefOr[Int] = js.undefined,
-    val maxmem: js.UndefOr[Int] = js.undefined
+    var cost: js.UndefOr[Int] = js.undefined,
+    var blockSize: js.UndefOr[Int] = js.undefined,
+    var parallelization: js.UndefOr[Int] = js.undefined,
+    var N: js.UndefOr[Int] = js.undefined,
+    var r: js.UndefOr[Int] = js.undefined,
+    var p: js.UndefOr[Int] = js.undefined,
+    var maxmem: js.UndefOr[Int] = js.undefined
 ) extends js.Object
 
 @js.native
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/crypto/Hash.scala b/app/current/src/main/scala/io/scalajs/nodejs/crypto/Hash.scala
index be2a28139..7688f78db 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/crypto/Hash.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/crypto/Hash.scala
@@ -53,7 +53,7 @@ sealed trait Hash extends Transform {
 
 }
 
-class CreateHashOptions(override val transform: js.UndefOr[js.Function] = js.undefined,
-                        override val flush: js.UndefOr[js.Function] = js.undefined,
-                        val outputLength: js.UndefOr[Int] = js.undefined)
+class CreateHashOptions(transform: js.UndefOr[js.Function] = js.undefined,
+                        flush: js.UndefOr[js.Function] = js.undefined,
+                        var outputLength: js.UndefOr[Int] = js.undefined)
     extends TransformOptions(transform, flush)
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/crypto/KeyObject.scala b/app/current/src/main/scala/io/scalajs/nodejs/crypto/KeyObject.scala
index d6006a463..7064b6089 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/crypto/KeyObject.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/crypto/KeyObject.scala
@@ -15,8 +15,8 @@ sealed trait KeyObject extends js.Object {
 }
 
 class KeyObjectExportOptions(
-    val `type`: js.UndefOr[String] = js.undefined,
-    val format: js.UndefOr[String] = js.undefined,
-    val cipher: js.UndefOr[String] = js.undefined,
-    val passphrase: js.UndefOr[String | Buffer] = js.undefined
+    var `type`: js.UndefOr[String] = js.undefined,
+    var format: js.UndefOr[String] = js.undefined,
+    var cipher: js.UndefOr[String] = js.undefined,
+    var passphrase: js.UndefOr[String | Buffer] = js.undefined
 ) extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/dns/TtlOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/dns/TtlOptions.scala
index de7e9c98f..ac6bb48b7 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/dns/TtlOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/dns/TtlOptions.scala
@@ -3,5 +3,5 @@ package io.scalajs.nodejs.dns
 import scala.scalajs.js
 
 class TtlOptions(
-    val ttl: js.UndefOr[Boolean] = js.undefined
+    var ttl: js.UndefOr[Boolean] = js.undefined
 ) extends js.Object {}
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/fs/FSWatcher.scala b/app/current/src/main/scala/io/scalajs/nodejs/fs/FSWatcher.scala
index 95825092f..d3ff86e72 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/fs/FSWatcher.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/fs/FSWatcher.scala
@@ -65,7 +65,7 @@ object FSWatcher {
   * @param recursive  Indicates whether all subdirectories should be watched, or only the current directory.
   *                   The applies when a directory is specified, and only on supported platforms (See Caveats) (default: false)
   */
-class FSWatcherOptions(val encoding: js.UndefOr[String] = js.undefined,
-                       val persistent: js.UndefOr[Boolean] = js.undefined,
-                       val recursive: js.UndefOr[Boolean] = js.undefined)
+class FSWatcherOptions(var encoding: js.UndefOr[String] = js.undefined,
+                       var persistent: js.UndefOr[Boolean] = js.undefined,
+                       var recursive: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/fs/Fs.scala b/app/current/src/main/scala/io/scalajs/nodejs/fs/Fs.scala
index 1734a7f12..3d23ad409 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/fs/Fs.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/fs/Fs.scala
@@ -1237,41 +1237,40 @@ trait BufferIOResult[T] extends js.Object {
 /**
   * File Append Options
   */
-class FileAppendOptions(val encoding: js.UndefOr[String] = js.undefined,
-                        val mode: js.UndefOr[FileMode] = js.undefined,
-                        val flag: js.UndefOr[String] = js.undefined)
+class FileAppendOptions(var encoding: js.UndefOr[String] = js.undefined,
+                        var mode: js.UndefOr[FileMode] = js.undefined,
+                        var flag: js.UndefOr[String] = js.undefined)
     extends js.Object
 
 /**
   * File Encoding Options
   */
-class FileEncodingOptions(val encoding: js.UndefOr[String] = js.undefined) extends js.Object
+class FileEncodingOptions(var encoding: js.UndefOr[String] = js.undefined) extends js.Object
 
-class ReaddirOptions(val encoding: js.UndefOr[String] = js.undefined,
-                     val withFileTypes: js.UndefOr[Boolean] = js.undefined)
+class ReaddirOptions(var encoding: js.UndefOr[String] = js.undefined,
+                     var withFileTypes: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
 
-class ReadFileOptions(val encoding: js.UndefOr[String] = js.undefined, val flag: js.UndefOr[String] = js.undefined)
+class ReadFileOptions(var flag: js.UndefOr[String] = js.undefined) extends js.Object
+
+class FileInputOptions(var flags: js.UndefOr[String] = js.undefined,
+                       var encoding: js.UndefOr[String] = js.undefined,
+                       var fd: js.UndefOr[FileDescriptor] = js.undefined,
+                       var mode: js.UndefOr[FileMode] = js.undefined,
+                       var autoClose: js.UndefOr[Boolean] = js.undefined,
+                       var emitClose: js.UndefOr[Boolean] = js.undefined,
+                       var start: js.UndefOr[Int] = js.undefined,
+                       var end: js.UndefOr[Int] = js.undefined,
+                       var highWaterMark: js.UndefOr[Int] = js.undefined)
     extends js.Object
 
-class FileInputOptions(val flags: js.UndefOr[String] = js.undefined,
-                       val encoding: js.UndefOr[String] = js.undefined,
-                       val fd: js.UndefOr[FileDescriptor] = js.undefined,
-                       val mode: js.UndefOr[FileMode] = js.undefined,
-                       val autoClose: js.UndefOr[Boolean] = js.undefined,
-                       val emitClose: js.UndefOr[Boolean] = js.undefined,
-                       val start: js.UndefOr[Int] = js.undefined,
-                       val end: js.UndefOr[Int] = js.undefined,
-                       val highWaterMark: js.UndefOr[Int] = js.undefined)
-    extends js.Object
-
-class FileOutputOptions(val flags: js.UndefOr[String] = js.undefined,
-                        val defaultEncoding: js.UndefOr[String] = js.undefined,
-                        val fd: js.UndefOr[FileDescriptor] = js.undefined,
-                        val mode: js.UndefOr[FileMode] = js.undefined,
-                        val autoClose: js.UndefOr[Boolean] = js.undefined,
-                        val emitClose: js.UndefOr[Boolean] = js.undefined,
-                        val start: js.UndefOr[Int] = js.undefined)
+class FileOutputOptions(var flags: js.UndefOr[String] = js.undefined,
+                        var defaultEncoding: js.UndefOr[String] = js.undefined,
+                        var fd: js.UndefOr[FileDescriptor] = js.undefined,
+                        var mode: js.UndefOr[FileMode] = js.undefined,
+                        var autoClose: js.UndefOr[Boolean] = js.undefined,
+                        var emitClose: js.UndefOr[Boolean] = js.undefined,
+                        var start: js.UndefOr[Int] = js.undefined)
     extends js.Object
 
 /**
@@ -1279,13 +1278,13 @@ class FileOutputOptions(val flags: js.UndefOr[String] = js.undefined,
   * @param persistent <Boolean>
   * @param interval   <Integer>
   */
-class FileWatcherOptions(val persistent: js.UndefOr[Boolean] = js.undefined,
-                         val interval: js.UndefOr[Int] = js.undefined)
+class FileWatcherOptions(var persistent: js.UndefOr[Boolean] = js.undefined,
+                         var interval: js.UndefOr[Int] = js.undefined)
     extends js.Object
 
-class StatOptions(val bigint: js.UndefOr[Boolean] = js.undefined) extends js.Object
+class StatOptions(var bigint: js.UndefOr[Boolean] = js.undefined) extends js.Object
 
-class MkdirOptions(val recursive: js.UndefOr[Boolean] = js.undefined, val mode: js.UndefOr[FileMode] = js.undefined)
+class MkdirOptions(var recursive: js.UndefOr[Boolean] = js.undefined, var mode: js.UndefOr[FileMode] = js.undefined)
     extends js.Object
 
 class RmdirOptions(var emfileWait: js.UndefOr[Int] = 1000,
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2SecureServerOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2SecureServerOptions.scala
index 563ef016c..1408eaa86 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2SecureServerOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2SecureServerOptions.scala
@@ -30,8 +30,8 @@ class Http2SecureServerOptions(
     var SNICallback: js.UndefOr[js.Function2[String, js.Function2[io.scalajs.nodejs.Error, SecureContext, Any], Any]],
     var ticketKeys: js.UndefOr[Buffer] = js.undefined,
 // Options for net.createServers
-    val allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
-    val pauseOnConnect: js.UndefOr[Boolean] = js.undefined,
+    var allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
+    var pauseOnConnect: js.UndefOr[Boolean] = js.undefined,
 // Options for tls.createSecureContext
     var ca: js.UndefOr[SecureData] = js.undefined,
     var cert: js.UndefOr[SecureData] = js.undefined,
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2ServerOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2ServerOptions.scala
index 46d3ce8a8..1e2a504f0 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2ServerOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/http2/Http2ServerOptions.scala
@@ -18,6 +18,6 @@ class Http2ServerOptions(
     var Http1ServerResponse: js.UndefOr[js.ConstructorTag[http.ServerResponse]] = js.undefined,
     var Http2ServerRequest: js.UndefOr[js.ConstructorTag[Http2ServerRequest]] = js.undefined,
     var Http2ServerResponse: js.UndefOr[js.ConstructorTag[Http2ServerResponse]] = js.undefined,
-    val allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
-    val pauseOnConnect: js.UndefOr[Boolean] = js.undefined
+    var allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
+    var pauseOnConnect: js.UndefOr[Boolean] = js.undefined
 ) extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/https/ServerOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/https/ServerOptions.scala
index f228424de..5a0b06576 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/https/ServerOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/https/ServerOptions.scala
@@ -19,8 +19,8 @@ class ServerOptions(
     var SNICallback: js.UndefOr[js.Function2[String, js.Function2[io.scalajs.nodejs.Error, SecureContext, Any], Any]],
     var ticketKeys: js.UndefOr[Buffer] = js.undefined,
     // Options for net.createServers
-    val allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
-    val pauseOnConnect: js.UndefOr[Boolean] = js.undefined,
+    var allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
+    var pauseOnConnect: js.UndefOr[Boolean] = js.undefined,
     // Options for tls.createSecureContext
     var ca: js.UndefOr[SecureData] = js.undefined,
     var cert: js.UndefOr[SecureData] = js.undefined,
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/net/ServerOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/net/ServerOptions.scala
index ec743ca36..344e4399c 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/net/ServerOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/net/ServerOptions.scala
@@ -2,6 +2,6 @@ package io.scalajs.nodejs.net
 
 import scala.scalajs.js
 
-class ServerOptions(val allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
-                    val pauseOnConnect: js.UndefOr[Boolean] = js.undefined)
+class ServerOptions(var allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
+                    var pauseOnConnect: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/net/SocketOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/net/SocketOptions.scala
index e15011d73..d1c520bcf 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/net/SocketOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/net/SocketOptions.scala
@@ -14,8 +14,8 @@ import scala.scalajs.js
   * @param readable
   * @param writable
   */
-class SocketOptions(val fd: js.UndefOr[FileDescriptor] = js.undefined,
-                    val allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
-                    val readable: js.UndefOr[Boolean] = js.undefined,
-                    val writable: js.UndefOr[Boolean] = js.undefined)
+class SocketOptions(var fd: js.UndefOr[FileDescriptor] = js.undefined,
+                    var allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
+                    var readable: js.UndefOr[Boolean] = js.undefined,
+                    var writable: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/path/PathObject.scala b/app/current/src/main/scala/io/scalajs/nodejs/path/PathObject.scala
index 0de7acd25..d9fee0c54 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/path/PathObject.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/path/PathObject.scala
@@ -5,9 +5,9 @@ import scala.scalajs.js
 /**
   * Path Object
   */
-class PathObject(val root: js.UndefOr[String] = js.undefined,
-                 val dir: js.UndefOr[String] = js.undefined,
-                 val base: js.UndefOr[String] = js.undefined,
-                 val ext: js.UndefOr[String] = js.undefined,
-                 val name: js.UndefOr[String] = js.undefined)
+class PathObject(var root: js.UndefOr[String] = js.undefined,
+                 var dir: js.UndefOr[String] = js.undefined,
+                 var base: js.UndefOr[String] = js.undefined,
+                 var ext: js.UndefOr[String] = js.undefined,
+                 var name: js.UndefOr[String] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/process/Process.scala b/app/current/src/main/scala/io/scalajs/nodejs/process/Process.scala
index 7b05c523b..fcefd5aac 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/process/Process.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/process/Process.scala
@@ -483,10 +483,10 @@ trait CpuUsage extends js.Object {
 }
 
 class WarningOptions(
-    val `type`: js.UndefOr[String] = js.undefined,
-    val code: js.UndefOr[String] = js.undefined,
-    val detail: js.UndefOr[String] = js.undefined,
-    val ctor: js.UndefOr[js.Function] = js.undefined
+    var `type`: js.UndefOr[String] = js.undefined,
+    var code: js.UndefOr[String] = js.undefined,
+    var detail: js.UndefOr[String] = js.undefined,
+    var ctor: js.UndefOr[js.Function] = js.undefined
 ) extends js.Object {}
 
 @js.native
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryDecodeOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryDecodeOptions.scala
index f171560cb..15d4f7a41 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryDecodeOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryDecodeOptions.scala
@@ -10,6 +10,6 @@ import scala.scalajs.js
   *                           key counting limitations. The querystring.parse() method parses a URL query string (str)
   *                           into a collection of key and value pairs.
   */
-class QueryDecodeOptions(val decodeURIComponent: js.UndefOr[js.Function] = js.undefined,
-                         val maxKeys: js.UndefOr[Int] = js.undefined)
+class QueryDecodeOptions(var decodeURIComponent: js.UndefOr[js.Function] = js.undefined,
+                         var maxKeys: js.UndefOr[Int] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryEncodeOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryEncodeOptions.scala
index 4d71e5d4b..fa91ff6b7 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryEncodeOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/querystring/QueryEncodeOptions.scala
@@ -7,4 +7,4 @@ import scala.scalajs.js
   * @param encodeURIComponent The function to use when converting URL-unsafe characters to percent-encoding in
   *                           the query string. Defaults to querystring.escape().
   */
-class QueryEncodeOptions(val encodeURIComponent: js.UndefOr[js.Function] = js.undefined) extends js.Object
+class QueryEncodeOptions(var encodeURIComponent: js.UndefOr[js.Function] = js.undefined) extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/stream/Stream.scala b/app/current/src/main/scala/io/scalajs/nodejs/stream/Stream.scala
index fcd915c38..130aaff41 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/stream/Stream.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/stream/Stream.scala
@@ -347,7 +347,7 @@ class ReadableOptions(
   * Readable Pipe Options
   * @param end End the writer when the reader ends. Defaults to true.
   */
-class ReadablePipeOptions(val end: js.UndefOr[Boolean] = js.undefined) extends js.Object
+class ReadablePipeOptions(var end: js.UndefOr[Boolean] = js.undefined) extends js.Object
 
 /**
   * Readable State
@@ -494,18 +494,18 @@ object IWritable {
   * @param chunk    the chunk of data
   * @param encoding the data's optional encoding
   */
-class Chunk(val chunk: Buffer | String, val encoding: js.UndefOr[String] = js.undefined) extends js.Object
-
-class WritableOptions(val highWaterMark: js.UndefOr[Int] = js.undefined,
-                      val decodeStrings: js.UndefOr[Boolean] = js.undefined,
-                      val defaultEncoding: js.UndefOr[String] = js.undefined,
-                      val objectMode: js.UndefOr[Boolean] = js.undefined,
-                      val emitClose: js.UndefOr[Boolean] = js.undefined,
-                      val write: js.UndefOr[js.Function] = js.undefined,
-                      val writev: js.UndefOr[js.Function] = js.undefined,
-                      val destroy: js.UndefOr[js.Function] = js.undefined,
-                      val `final`: js.UndefOr[js.Function] = js.undefined,
-                      val autoDestroy: js.UndefOr[Boolean] = js.undefined)
+class Chunk(var encoding: js.UndefOr[String] = js.undefined) extends js.Object
+
+class WritableOptions(var highWaterMark: js.UndefOr[Int] = js.undefined,
+                      var decodeStrings: js.UndefOr[Boolean] = js.undefined,
+                      var defaultEncoding: js.UndefOr[String] = js.undefined,
+                      var objectMode: js.UndefOr[Boolean] = js.undefined,
+                      var emitClose: js.UndefOr[Boolean] = js.undefined,
+                      var write: js.UndefOr[js.Function] = js.undefined,
+                      var writev: js.UndefOr[js.Function] = js.undefined,
+                      var destroy: js.UndefOr[js.Function] = js.undefined,
+                      var `final`: js.UndefOr[js.Function] = js.undefined,
+                      var autoDestroy: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
 
 /**
@@ -533,6 +533,6 @@ class DuplexOptions(var allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
                     var writableObjectMode: js.UndefOr[Boolean] = js.undefined)
     extends js.Object
 
-class TransformOptions(val transform: js.UndefOr[js.Function] = js.undefined,
-                       val flush: js.UndefOr[js.Function] = js.undefined)
+class TransformOptions(var transform: js.UndefOr[js.Function] = js.undefined,
+                       var flush: js.UndefOr[js.Function] = js.undefined)
     extends js.Object
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/tls/ServerOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/tls/ServerOptions.scala
index 61e96ed92..f4a1cc727 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/tls/ServerOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/tls/ServerOptions.scala
@@ -18,8 +18,8 @@ class ServerOptions(
     var SNICallback: js.UndefOr[js.Function2[String, js.Function2[io.scalajs.nodejs.Error, SecureContext, Any], Any]],
     var ticketKeys: js.UndefOr[Buffer] = js.undefined,
     // Options for net.createServers
-    val allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
-    val pauseOnConnect: js.UndefOr[Boolean] = js.undefined,
+    var allowHalfOpen: js.UndefOr[Boolean] = js.undefined,
+    var pauseOnConnect: js.UndefOr[Boolean] = js.undefined,
     // Options for tls.createSecureContext
     var ca: js.UndefOr[SecureData] = js.undefined,
     var cert: js.UndefOr[SecureData] = js.undefined,
diff --git a/app/current/src/main/scala/io/scalajs/nodejs/url/UrlFormatOptions.scala b/app/current/src/main/scala/io/scalajs/nodejs/url/UrlFormatOptions.scala
index 342465f55..b1409b023 100644
--- a/app/current/src/main/scala/io/scalajs/nodejs/url/UrlFormatOptions.scala
+++ b/app/current/src/main/scala/io/scalajs/nodejs/url/UrlFormatOptions.scala
@@ -11,8 +11,8 @@ import scala.scalajs.js
   * @param unicode  true if Unicode characters appearing in the host component of the URL string should be encoded
   *                 directly as opposed to being Punycode encoded. Defaults to false.
   */
-class UrlFormatOptions(val auth: js.UndefOr[Boolean] = js.undefined,
-                       val fragment: js.UndefOr[Boolean] = js.undefined,
-                       val search: js.UndefOr[Boolean] = js.undefined,
-                       val unicode: js.UndefOr[Boolean] = js.undefined)
+class UrlFormatOptions(var auth: js.UndefOr[Boolean] = js.undefined,
+                       var fragment: js.UndefOr[Boolean] = js.undefined,
+                       var search: js.UndefOr[Boolean] = js.undefined,
+                       var unicode: js.UndefOr[Boolean] = js.undefined)
     extends js.Object