diff --git a/js/src/tests/ecma_6/Symbol/toStringTag.js b/js/src/tests/ecma_6/Symbol/toStringTag.js
index 9ff0d7fefa81..20aac2c42c48 100644
--- a/js/src/tests/ecma_6/Symbol/toStringTag.js
+++ b/js/src/tests/ecma_6/Symbol/toStringTag.js
@@ -149,4 +149,7 @@ testDefault(function* () {}().__proto__.__proto__, "Generator");
 // ES6 25.4.5.4 Promise.prototype [ @@toStringTag ]
 testDefault(Promise.prototype, "Promise");
 
+// AsyncFunction.prototype [ @@toStringTag ]
+testDefault(async function() {}.constructor.prototype, "AsyncFunction");
+
 reportCompare(true, true);
diff --git a/js/src/vm/AsyncFunction.cpp b/js/src/vm/AsyncFunction.cpp
index 496b2750fc21..a0a3cfac0763 100644
--- a/js/src/vm/AsyncFunction.cpp
+++ b/js/src/vm/AsyncFunction.cpp
@@ -25,6 +25,9 @@ GlobalObject::initAsyncFunction(JSContext* cx, Handle<GlobalObject*> global)
     if (!asyncFunctionProto)
         return false;
 
+    if (!DefineToStringTag(cx, asyncFunctionProto, cx->names().AsyncFunction))
+        return false;
+
     RootedValue function(cx, global->getConstructor(JSProto_Function));
     if (!function.toObjectOrNull())
         return false;