diff --git a/src/services/codefixes/helpers.ts b/src/services/codefixes/helpers.ts
index 19fb41ceeb029..89cf008adad80 100644
--- a/src/services/codefixes/helpers.ts
+++ b/src/services/codefixes/helpers.ts
@@ -400,7 +400,7 @@ export function createSignatureDeclarationFromSignature(
                 parameterDecl.modifiers,
                 parameterDecl.dotDotDotToken,
                 parameterDecl.name,
-                parameterDecl.questionToken,
+                isJs ? undefined : parameterDecl.questionToken,
                 type,
                 parameterDecl.initializer
             );
diff --git a/tests/cases/fourslash/codeFixAddMissingProperties26.ts b/tests/cases/fourslash/codeFixAddMissingProperties26.ts
new file mode 100644
index 0000000000000..f742b139d3265
--- /dev/null
+++ b/tests/cases/fourslash/codeFixAddMissingProperties26.ts
@@ -0,0 +1,20 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+// @checkJs: true
+// @filename: /a.js
+/////**
+//// * @type {{ f: (x?: string) => number }}
+//// */
+////[|export const foo = {}|]
+
+verify.codeFix({
+    index: 0,
+    description: ts.Diagnostics.Add_missing_properties.message,
+    newRangeContent:
+`export const foo = {
+    f: function(x) {
+        throw new Error("Function not implemented.");
+    }
+}`,
+});