diff --git a/packages/@ember/-internals/glimmer/lib/helpers/fn.ts b/packages/@ember/-internals/glimmer/lib/helpers/fn.ts
index 63a3f7e87d5..7c4dca12077 100644
--- a/packages/@ember/-internals/glimmer/lib/helpers/fn.ts
+++ b/packages/@ember/-internals/glimmer/lib/helpers/fn.ts
@@ -98,7 +98,7 @@ export default function (args: VMArguments) {
         if (DEBUG) assertCallbackIsFn(callbackRef);
 
         if (isInvokableRef(callbackRef)) {
-          let value = args[0] || invocationArgs[0];
+          let value = args.length > 0 ? args[0] : invocationArgs[0];
           return updateRef(callbackRef, value);
         } else {
           return (fn as Function).call(context, ...args, ...invocationArgs);
diff --git a/packages/@ember/-internals/glimmer/tests/integration/helpers/fn-test.js b/packages/@ember/-internals/glimmer/tests/integration/helpers/fn-test.js
index 7a3f6c9cdc1..6b9986d3547 100644
--- a/packages/@ember/-internals/glimmer/tests/integration/helpers/fn-test.js
+++ b/packages/@ember/-internals/glimmer/tests/integration/helpers/fn-test.js
@@ -244,5 +244,18 @@ moduleFor(
 
       this.assertText('bar');
     }
+
+    '@test can be used on the result of `mut` with a falsy value'() {
+      this.render(`{{this.arg1}}{{stash stashedFn=(fn (mut this.arg1) this.arg2)}}`, {
+        arg1: 'foo',
+        arg2: false,
+      });
+
+      this.assertText('foo');
+
+      runTask(() => this.stashedFn());
+
+      this.assertText('false');
+    }
   }
 );