diff --git a/packages/@ember/-internals/glimmer/lib/helpers/mut.ts b/packages/@ember/-internals/glimmer/lib/helpers/mut.ts
index 019e7e3ac4b..9b7d5f91b61 100644
--- a/packages/@ember/-internals/glimmer/lib/helpers/mut.ts
+++ b/packages/@ember/-internals/glimmer/lib/helpers/mut.ts
@@ -139,7 +139,7 @@ export default function(args: VMArguments, vm: VM) {
   //
   // This message is alright for the first case, but could be quite
   // confusing for the second case.
-  assert('You can only pass a path to mut', UPDATE_REFERENCED_VALUE in rawRef);
+  assert('You can only pass a path to mut', rawRef[UPDATE_REFERENCED_VALUE] !== undefined);
 
   return new MutReference(rawRef, vm.env);
 }
diff --git a/packages/@ember/-internals/glimmer/lib/utils/iterator.ts b/packages/@ember/-internals/glimmer/lib/utils/iterator.ts
index 2b3d267ba3f..7b6bbb67fc9 100644
--- a/packages/@ember/-internals/glimmer/lib/utils/iterator.ts
+++ b/packages/@ember/-internals/glimmer/lib/utils/iterator.ts
@@ -150,7 +150,8 @@ class ObjectIterator extends BoundedIterator {
     let length = 0;
     let isMapLike = false;
 
-    obj.forEach((value: unknown, key: unknown) => {
+    // Not using an arrow function here so we can get an accurate `arguments`
+    obj.forEach(function (value: unknown, key: unknown) {
       isMapLike = isMapLike || arguments.length >= 2;
 
       if (isMapLike) {
diff --git a/packages/@ember/-internals/glimmer/tests/integration/helpers/tracked-test.js b/packages/@ember/-internals/glimmer/tests/integration/helpers/tracked-test.js
index 23e5e077950..fe81f543951 100644
--- a/packages/@ember/-internals/glimmer/tests/integration/helpers/tracked-test.js
+++ b/packages/@ember/-internals/glimmer/tests/integration/helpers/tracked-test.js
@@ -353,7 +353,7 @@ moduleFor(
       });
 
       let expectedMessage = backtrackingMessageFor('name', '\\(unknown object\\)', {
-        renderTree: ['\\(result of a `helloWorld` helper\\)'],
+        renderTree: ['\\(result of a `.*` helper\\)'],
       });
 
       expectDeprecation(() => {
diff --git a/yarn.lock b/yarn.lock
index 494062ff8d1..d777f096883 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4447,18 +4447,7 @@ growly@^1.3.0:
   resolved "https://registry.yarnpkg.com/growly/-/growly-1.3.0.tgz#f10748cbe76af964b7c96c93c6bcc28af120c081"
   integrity sha1-8QdIy+dq+WS3yWyTxrzCivEgwIE=
 
-handlebars@^4.0.11, handlebars@^4.0.4, handlebars@^4.0.6:
-  version "4.5.3"
-  resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.5.3.tgz#5cf75bd8714f7605713511a56be7c349becb0482"
-  integrity sha512-3yPecJoJHK/4c6aZhSvxOyG4vJKDshV36VHp0iVCDVh7o9w2vwi3NSnL2MMPj3YdduqaBcu7cGbggJQM0br9xA==
-  dependencies:
-    neo-async "^2.6.0"
-    optimist "^0.6.1"
-    source-map "^0.6.1"
-  optionalDependencies:
-    uglify-js "^3.1.4"
-
-handlebars@^4.5.1:
+handlebars@^4.0.11, handlebars@^4.0.4, handlebars@^4.5.1:
   version "4.5.3"
   resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.5.3.tgz#5cf75bd8714f7605713511a56be7c349becb0482"
   integrity sha512-3yPecJoJHK/4c6aZhSvxOyG4vJKDshV36VHp0iVCDVh7o9w2vwi3NSnL2MMPj3YdduqaBcu7cGbggJQM0br9xA==