--- a/xpcom/glue/tests/gtest/TestThreadUtils.cpp
+++ b/xpcom/glue/tests/gtest/TestThreadUtils.cpp
@@ -175,17 +175,23 @@ public:
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_IFOO_IID)
 
   NS_IMETHOD_(nsrefcnt) RefCnt() = 0;
   NS_IMETHOD_(int32_t) ID() = 0;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(IThreadUtilsObject, NS_IFOO_IID)
 
+struct ThreadUtilsObjectNonRefCountedBase
+{
+  virtual void MethodFromNonRefCountedBase() {}
+};
+
 struct ThreadUtilsObject : public IThreadUtilsObject
+                         , public ThreadUtilsObjectNonRefCountedBase
 {
   // nsISupports implementation
   NS_DECL_ISUPPORTS
 
   // IThreadUtilsObject implementation
   NS_IMETHOD_(nsrefcnt) RefCnt() override { return mRefCnt; }
   NS_IMETHOD_(int32_t) ID() override { return 0; }
 
@@ -369,16 +375,22 @@ TEST(ThreadUtils, main)
   r1->Run();
   EXPECT_EQ(count += 1, rpt->mCount);
 
   r1 = NewRunnableMethod<int>(rpt, &ThreadUtilsObject::Test1i, 11);
   r1->Run();
   EXPECT_EQ(count += 2, rpt->mCount);
   EXPECT_EQ(11, rpt->mA0);
 
+  // Test calling a method from a non-ref-counted base.
+
+  r1 = NewRunnableMethod(rpt, &ThreadUtilsObject::MethodFromNonRefCountedBase);
+  r1->Run();
+  EXPECT_EQ(count, rpt->mCount);
+
   // Test variadic function with simple POD arguments.
 
   r1 = NewRunnableMethod(rpt, &ThreadUtilsObject::Test0);
   r1->Run();
   EXPECT_EQ(count += 1, rpt->mCount);
 
   static_assert(
       mozilla::IsSame< ::detail::ParameterStorage<int>::Type,