diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 6314f98bcff7c..69f4983ca72bd 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -319,6 +319,7 @@ namespace ts {
 
         const globalThisSymbol = createSymbol(SymbolFlags.Module, "globalThis" as __String, CheckFlags.Readonly);
         globalThisSymbol.exports = globals;
+        globalThisSymbol.declarations = [];
         globals.set(globalThisSymbol.escapedName, globalThisSymbol);
 
         const argumentsSymbol = createSymbol(SymbolFlags.Property, "arguments" as __String);
diff --git a/tests/baselines/reference/extendGlobalThis.symbols b/tests/baselines/reference/extendGlobalThis.symbols
index 944d7b237157b..91cd0bf2530c3 100644
--- a/tests/baselines/reference/extendGlobalThis.symbols
+++ b/tests/baselines/reference/extendGlobalThis.symbols
@@ -3,7 +3,7 @@ declare global {
 >global : Symbol(global, Decl(extension.d.ts, 0, 0))
 
     namespace globalThis  {
->globalThis : Symbol(globalThis)
+>globalThis : Symbol(globalThis, Decl(extension.d.ts, 0, 16))
 
         var test: string;
 >test : Symbol(test, Decl(extension.d.ts, 2, 11))
@@ -16,7 +16,7 @@ export {}
 import "./extention";
 
 globalThis.tests = "a-b";
->globalThis : Symbol(globalThis)
+>globalThis : Symbol(globalThis, Decl(extension.d.ts, 0, 16))
 
 console.log(globalThis.test.split("-"));
 >console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
@@ -24,7 +24,7 @@ console.log(globalThis.test.split("-"));
 >log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
 >globalThis.test.split : Symbol(String.split, Decl(lib.es5.d.ts, --, --))
 >globalThis.test : Symbol(test, Decl(extension.d.ts, 2, 11))
->globalThis : Symbol(globalThis)
+>globalThis : Symbol(globalThis, Decl(extension.d.ts, 0, 16))
 >test : Symbol(test, Decl(extension.d.ts, 2, 11))
 >split : Symbol(String.split, Decl(lib.es5.d.ts, --, --))
 
diff --git a/tests/baselines/reference/extendGlobalThis2.errors.txt b/tests/baselines/reference/extendGlobalThis2.errors.txt
new file mode 100644
index 0000000000000..09e78cba92da8
--- /dev/null
+++ b/tests/baselines/reference/extendGlobalThis2.errors.txt
@@ -0,0 +1,10 @@
+tests/cases/compiler/extendGlobalThis2.ts(1,11): error TS2397: Declaration name conflicts with built-in global identifier 'globalThis'.
+
+
+==== tests/cases/compiler/extendGlobalThis2.ts (1 errors) ====
+    namespace globalThis {
+              ~~~~~~~~~~
+!!! error TS2397: Declaration name conflicts with built-in global identifier 'globalThis'.
+        export function foo() { console.log("x"); }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/extendGlobalThis2.js b/tests/baselines/reference/extendGlobalThis2.js
new file mode 100644
index 0000000000000..63f06536ce516
--- /dev/null
+++ b/tests/baselines/reference/extendGlobalThis2.js
@@ -0,0 +1,12 @@
+//// [extendGlobalThis2.ts]
+namespace globalThis {
+    export function foo() { console.log("x"); }
+}
+
+
+//// [extendGlobalThis2.js]
+var globalThis;
+(function (globalThis) {
+    function foo() { console.log("x"); }
+    globalThis.foo = foo;
+})(globalThis || (globalThis = {}));
diff --git a/tests/baselines/reference/extendGlobalThis2.symbols b/tests/baselines/reference/extendGlobalThis2.symbols
new file mode 100644
index 0000000000000..f16727a674b4e
--- /dev/null
+++ b/tests/baselines/reference/extendGlobalThis2.symbols
@@ -0,0 +1,11 @@
+=== tests/cases/compiler/extendGlobalThis2.ts ===
+namespace globalThis {
+>globalThis : Symbol(globalThis, Decl(extendGlobalThis2.ts, 0, 0))
+
+    export function foo() { console.log("x"); }
+>foo : Symbol(foo, Decl(extendGlobalThis2.ts, 0, 22))
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+}
+
diff --git a/tests/baselines/reference/extendGlobalThis2.types b/tests/baselines/reference/extendGlobalThis2.types
new file mode 100644
index 0000000000000..4a06219474245
--- /dev/null
+++ b/tests/baselines/reference/extendGlobalThis2.types
@@ -0,0 +1,13 @@
+=== tests/cases/compiler/extendGlobalThis2.ts ===
+namespace globalThis {
+>globalThis : typeof globalThis
+
+    export function foo() { console.log("x"); }
+>foo : () => void
+>console.log("x") : void
+>console.log : (message?: any, ...optionalParams: any[]) => void
+>console : Console
+>log : (message?: any, ...optionalParams: any[]) => void
+>"x" : "x"
+}
+
diff --git a/tests/baselines/reference/globalThisPropertyAssignment.symbols b/tests/baselines/reference/globalThisPropertyAssignment.symbols
index 1ae4dd5af6387..3bc852cbba175 100644
--- a/tests/baselines/reference/globalThisPropertyAssignment.symbols
+++ b/tests/baselines/reference/globalThisPropertyAssignment.symbols
@@ -1,7 +1,7 @@
 === tests/cases/conformance/es2019/globalThisPropertyAssignment.js ===
 this.x = 1
 >this.x : Symbol(x, Decl(globalThisPropertyAssignment.js, 0, 0))
->this : Symbol(globalThis)
+>this : Symbol(globalThis, Decl(globalThisPropertyAssignment.js, 3, 12))
 >x : Symbol(x, Decl(globalThisPropertyAssignment.js, 0, 0))
 
 var y = 2
@@ -14,6 +14,6 @@ window.z = 3
 // should work in JS (even though it's a secondary declaration)
 globalThis.alpha = 4
 >globalThis.alpha : Symbol(alpha, Decl(globalThisPropertyAssignment.js, 3, 12))
->globalThis : Symbol(globalThis)
+>globalThis : Symbol(globalThis, Decl(globalThisPropertyAssignment.js, 3, 12))
 >alpha : Symbol(alpha, Decl(globalThisPropertyAssignment.js, 3, 12))
 
diff --git a/tests/cases/compiler/extendGlobalThis2.ts b/tests/cases/compiler/extendGlobalThis2.ts
new file mode 100644
index 0000000000000..4949c91cf22eb
--- /dev/null
+++ b/tests/cases/compiler/extendGlobalThis2.ts
@@ -0,0 +1,3 @@
+namespace globalThis {
+    export function foo() { console.log("x"); }
+}