diff --git a/src/harness/vfsUtil.ts b/src/harness/vfsUtil.ts
index 4799927a70a14..596575beece2c 100644
--- a/src/harness/vfsUtil.ts
+++ b/src/harness/vfsUtil.ts
@@ -637,7 +637,7 @@ export class FileSystem {
      *
      * NOTE: do not rename this method as it is intended to align with the same named export of the "fs" module.
      */
-    public readFileSync(path: string, encoding?: null): Buffer; // eslint-disable-line no-restricted-syntax
+    public readFileSync(path: string, encoding?: null): Buffer<ArrayBuffer>; // eslint-disable-line no-restricted-syntax
     /**
      * Read from a file.
      *
@@ -649,7 +649,7 @@ export class FileSystem {
      *
      * NOTE: do not rename this method as it is intended to align with the same named export of the "fs" module.
      */
-    public readFileSync(path: string, encoding?: BufferEncoding | null): string | Buffer; // eslint-disable-line no-restricted-syntax
+    public readFileSync(path: string, encoding?: BufferEncoding | null): string | Buffer<ArrayBuffer>; // eslint-disable-line no-restricted-syntax
     public readFileSync(path: string, encoding: BufferEncoding | null = null) { // eslint-disable-line no-restricted-syntax
         const { node } = this._walk(this._resolve(path));
         if (!node) throw createIOError("ENOENT");
diff --git a/src/lib/es2015.symbol.wellknown.d.ts b/src/lib/es2015.symbol.wellknown.d.ts
index ed5d1ddbb388f..1ab84be969fca 100644
--- a/src/lib/es2015.symbol.wellknown.d.ts
+++ b/src/lib/es2015.symbol.wellknown.d.ts
@@ -251,7 +251,7 @@ interface String {
 }
 
 interface ArrayBuffer {
-    readonly [Symbol.toStringTag]: string;
+    readonly [Symbol.toStringTag]: "ArrayBuffer";
 }
 
 interface DataView<TArrayBuffer extends ArrayBufferLike> {
diff --git a/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.errors.txt b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.errors.txt
new file mode 100644
index 0000000000000..cc22119ec5064
--- /dev/null
+++ b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.errors.txt
@@ -0,0 +1,11 @@
+assignSharedArrayBufferToArrayBuffer.ts(1,5): error TS2322: Type 'SharedArrayBuffer' is not assignable to type 'ArrayBuffer'.
+  Types of property '[Symbol.toStringTag]' are incompatible.
+    Type '"SharedArrayBuffer"' is not assignable to type '"ArrayBuffer"'.
+
+
+==== assignSharedArrayBufferToArrayBuffer.ts (1 errors) ====
+    var foo: ArrayBuffer = new SharedArrayBuffer(1024); // should error
+        ~~~
+!!! error TS2322: Type 'SharedArrayBuffer' is not assignable to type 'ArrayBuffer'.
+!!! error TS2322:   Types of property '[Symbol.toStringTag]' are incompatible.
+!!! error TS2322:     Type '"SharedArrayBuffer"' is not assignable to type '"ArrayBuffer"'.
\ No newline at end of file
diff --git a/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.js b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.js
new file mode 100644
index 0000000000000..f7642aae6275d
--- /dev/null
+++ b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.js
@@ -0,0 +1,7 @@
+//// [tests/cases/conformance/es2017/assignSharedArrayBufferToArrayBuffer.ts] ////
+
+//// [assignSharedArrayBufferToArrayBuffer.ts]
+var foo: ArrayBuffer = new SharedArrayBuffer(1024); // should error
+
+//// [assignSharedArrayBufferToArrayBuffer.js]
+var foo = new SharedArrayBuffer(1024); // should error
diff --git a/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.symbols b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.symbols
new file mode 100644
index 0000000000000..43cfb5a1787b0
--- /dev/null
+++ b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.symbols
@@ -0,0 +1,8 @@
+//// [tests/cases/conformance/es2017/assignSharedArrayBufferToArrayBuffer.ts] ////
+
+=== assignSharedArrayBufferToArrayBuffer.ts ===
+var foo: ArrayBuffer = new SharedArrayBuffer(1024); // should error
+>foo : Symbol(foo, Decl(assignSharedArrayBufferToArrayBuffer.ts, 0, 3))
+>ArrayBuffer : Symbol(ArrayBuffer, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+>SharedArrayBuffer : Symbol(SharedArrayBuffer, Decl(lib.es2017.sharedmemory.d.ts, --, --), Decl(lib.es2017.sharedmemory.d.ts, --, --))
+
diff --git a/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.types b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.types
new file mode 100644
index 0000000000000..1f6b881dfb452
--- /dev/null
+++ b/tests/baselines/reference/assignSharedArrayBufferToArrayBuffer.types
@@ -0,0 +1,13 @@
+//// [tests/cases/conformance/es2017/assignSharedArrayBufferToArrayBuffer.ts] ////
+
+=== assignSharedArrayBufferToArrayBuffer.ts ===
+var foo: ArrayBuffer = new SharedArrayBuffer(1024); // should error
+>foo : ArrayBuffer
+>    : ^^^^^^^^^^^
+>new SharedArrayBuffer(1024) : SharedArrayBuffer
+>                            : ^^^^^^^^^^^^^^^^^
+>SharedArrayBuffer : SharedArrayBufferConstructor
+>                  : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+>1024 : 1024
+>     : ^^^^
+
diff --git a/tests/cases/conformance/es2017/assignSharedArrayBufferToArrayBuffer.ts b/tests/cases/conformance/es2017/assignSharedArrayBufferToArrayBuffer.ts
new file mode 100644
index 0000000000000..f0a38d9ee04f4
--- /dev/null
+++ b/tests/cases/conformance/es2017/assignSharedArrayBufferToArrayBuffer.ts
@@ -0,0 +1,4 @@
+// @target: es5
+// @lib: es2015,es2017.sharedmemory
+
+var foo: ArrayBuffer = new SharedArrayBuffer(1024); // should error
\ No newline at end of file