diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 3c0f714ede0..00bf031c183 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -3213,7 +3213,9 @@ function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
                     declareSymbolAndAddToSymbolTable(node, SymbolFlags.FunctionScopedVariable, SymbolFlags.FunctionScopedVariableExcludes);
                 }
                 break;
-
+            // Namespaces are not allowed in javascript files, so do nothing here
+            case SyntaxKind.ModuleDeclaration:
+                break;
             default:
                 Debug.failBadSyntaxKind(thisContainer);
         }
diff --git a/tests/baselines/reference/moduleCrashInJSFile.errors.txt b/tests/baselines/reference/moduleCrashInJSFile.errors.txt
new file mode 100644
index 00000000000..1dba2131d2f
--- /dev/null
+++ b/tests/baselines/reference/moduleCrashInJSFile.errors.txt
@@ -0,0 +1,25 @@
+tests/cases/compiler/a.js(2,8): error TS2300: Duplicate identifier 'foo'.
+tests/cases/compiler/a.js(2,8): error TS8006: 'module' declarations can only be used in TypeScript files.
+tests/cases/compiler/a.js(3,5): error TS2331: 'this' cannot be referenced in a module or namespace body.
+tests/cases/compiler/a.js(7,5): error TS2300: Duplicate identifier 'foo'.
+
+
+==== tests/cases/compiler/a.js (4 errors) ====
+    //// [thisKeyword.ts]
+    module foo {
+           ~~~
+!!! error TS2300: Duplicate identifier 'foo'.
+           ~~~
+!!! error TS8006: 'module' declarations can only be used in TypeScript files.
+        this.bar = 4;
+        ~~~~
+!!! error TS2331: 'this' cannot be referenced in a module or namespace body.
+    }
+    
+    //// [thisKeyword.js]
+    var foo;
+        ~~~
+!!! error TS2300: Duplicate identifier 'foo'.
+    (function (foo) {
+        this.bar = 4;
+    })(foo || (foo = {}));
\ No newline at end of file
diff --git a/tests/baselines/reference/moduleCrashInJSFile.js b/tests/baselines/reference/moduleCrashInJSFile.js
new file mode 100644
index 00000000000..fb87e04c8f0
--- /dev/null
+++ b/tests/baselines/reference/moduleCrashInJSFile.js
@@ -0,0 +1,23 @@
+//// [a.js]
+//// [thisKeyword.ts]
+module foo {
+    this.bar = 4;
+}
+
+//// [thisKeyword.js]
+var foo;
+(function (foo) {
+    this.bar = 4;
+})(foo || (foo = {}));
+
+//// [a.js]
+//// [thisKeyword.ts]
+var foo;
+(function (foo) {
+    this.bar = 4;
+})(foo || (foo = {}));
+//// [thisKeyword.js]
+var foo;
+(function (foo) {
+    this.bar = 4;
+})(foo || (foo = {}));
diff --git a/tests/baselines/reference/moduleCrashInJSFile.symbols b/tests/baselines/reference/moduleCrashInJSFile.symbols
new file mode 100644
index 00000000000..0056d1cf887
--- /dev/null
+++ b/tests/baselines/reference/moduleCrashInJSFile.symbols
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/a.js ===
+//// [thisKeyword.ts]
+module foo {
+>foo : Symbol(foo, Decl(a.js, 0, 0))
+
+    this.bar = 4;
+}
+
+//// [thisKeyword.js]
+var foo;
+>foo : Symbol(foo, Decl(a.js, 6, 3))
+
+(function (foo) {
+>foo : Symbol(foo, Decl(a.js, 7, 11))
+
+    this.bar = 4;
+>this.bar : Symbol((Anonymous function).bar, Decl(a.js, 7, 17))
+>this : Symbol((Anonymous function), Decl(a.js, 7, 1))
+>bar : Symbol((Anonymous function).bar, Decl(a.js, 7, 17))
+
+})(foo || (foo = {}));
+>foo : Symbol(foo, Decl(a.js, 0, 0))
+>foo : Symbol(foo, Decl(a.js, 0, 0))
+
diff --git a/tests/baselines/reference/moduleCrashInJSFile.types b/tests/baselines/reference/moduleCrashInJSFile.types
new file mode 100644
index 00000000000..a9d034ca3f4
--- /dev/null
+++ b/tests/baselines/reference/moduleCrashInJSFile.types
@@ -0,0 +1,38 @@
+=== tests/cases/compiler/a.js ===
+//// [thisKeyword.ts]
+module foo {
+>foo : typeof foo
+
+    this.bar = 4;
+>this.bar = 4 : 4
+>this.bar : any
+>this : any
+>bar : any
+>4 : 4
+}
+
+//// [thisKeyword.js]
+var foo;
+>foo : any
+
+(function (foo) {
+>(function (foo) {    this.bar = 4;})(foo || (foo = {})) : void
+>(function (foo) {    this.bar = 4;}) : typeof (Anonymous function)
+>function (foo) {    this.bar = 4;} : typeof (Anonymous function)
+>foo : typeof globalThis.foo
+
+    this.bar = 4;
+>this.bar = 4 : 4
+>this.bar : any
+>this : this
+>bar : any
+>4 : 4
+
+})(foo || (foo = {}));
+>foo || (foo = {}) : typeof foo
+>foo : typeof foo
+>(foo = {}) : {}
+>foo = {} : {}
+>foo : typeof foo
+>{} : {}
+
diff --git a/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.errors.txt b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.errors.txt
new file mode 100644
index 00000000000..2706b6ef60b
--- /dev/null
+++ b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.errors.txt
@@ -0,0 +1,24 @@
+tests/cases/compiler/a.js(1,8): error TS8006: 'module' declarations can only be used in TypeScript files.
+tests/cases/compiler/a.js(2,5): error TS2331: 'this' cannot be referenced in a module or namespace body.
+tests/cases/compiler/b.js(1,11): error TS8006: 'namespace' declarations can only be used in TypeScript files.
+tests/cases/compiler/b.js(2,5): error TS2331: 'this' cannot be referenced in a module or namespace body.
+
+
+==== tests/cases/compiler/a.js (2 errors) ====
+    module foo {
+           ~~~
+!!! error TS8006: 'module' declarations can only be used in TypeScript files.
+        this.bar = 4;
+        ~~~~
+!!! error TS2331: 'this' cannot be referenced in a module or namespace body.
+    }
+    
+==== tests/cases/compiler/b.js (2 errors) ====
+    namespace blah {
+              ~~~~
+!!! error TS8006: 'namespace' declarations can only be used in TypeScript files.
+        this.prop = 42;
+        ~~~~
+!!! error TS2331: 'this' cannot be referenced in a module or namespace body.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.js b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.js
new file mode 100644
index 00000000000..4735d38fdef
--- /dev/null
+++ b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.js
@@ -0,0 +1,23 @@
+//// [tests/cases/compiler/thisAssignmentInNamespaceDeclaration1.ts] ////
+
+//// [a.js]
+module foo {
+    this.bar = 4;
+}
+
+//// [b.js]
+namespace blah {
+    this.prop = 42;
+}
+
+
+//// [a.js]
+var foo;
+(function (foo) {
+    this.bar = 4;
+})(foo || (foo = {}));
+//// [b.js]
+var blah;
+(function (blah) {
+    this.prop = 42;
+})(blah || (blah = {}));
diff --git a/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.symbols b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.symbols
new file mode 100644
index 00000000000..5ada23b2237
--- /dev/null
+++ b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.symbols
@@ -0,0 +1,14 @@
+=== tests/cases/compiler/a.js ===
+module foo {
+>foo : Symbol(foo, Decl(a.js, 0, 0))
+
+    this.bar = 4;
+}
+
+=== tests/cases/compiler/b.js ===
+namespace blah {
+>blah : Symbol(blah, Decl(b.js, 0, 0))
+
+    this.prop = 42;
+}
+
diff --git a/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.types b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.types
new file mode 100644
index 00000000000..3ec8db55634
--- /dev/null
+++ b/tests/baselines/reference/thisAssignmentInNamespaceDeclaration1.types
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/a.js ===
+module foo {
+>foo : typeof foo
+
+    this.bar = 4;
+>this.bar = 4 : 4
+>this.bar : any
+>this : any
+>bar : any
+>4 : 4
+}
+
+=== tests/cases/compiler/b.js ===
+namespace blah {
+>blah : typeof blah
+
+    this.prop = 42;
+>this.prop = 42 : 42
+>this.prop : any
+>this : any
+>prop : any
+>42 : 42
+}
+
diff --git a/tests/cases/compiler/thisAssignmentInNamespaceDeclaration1.ts b/tests/cases/compiler/thisAssignmentInNamespaceDeclaration1.ts
new file mode 100644
index 00000000000..4f17a3432d4
--- /dev/null
+++ b/tests/cases/compiler/thisAssignmentInNamespaceDeclaration1.ts
@@ -0,0 +1,12 @@
+// @checkJs: true
+// @outDir: out/
+
+// @filename: a.js
+module foo {
+    this.bar = 4;
+}
+
+// @filename: b.js
+namespace blah {
+    this.prop = 42;
+}