--- a/mfbt/ThreadLocal.h
+++ b/mfbt/ThreadLocal.h
@@ -232,17 +232,17 @@ ThreadLocal<T, Storage>::set(const T aVa
 {
   MOZ_ASSERT(Storage<T>::initialized());
   bool succeeded = Storage<T>::set(aValue);
   if (!succeeded) {
     MOZ_CRASH();
   }
 }
 
-#if defined(XP_WIN) || defined(MACOSX_HAS_THREAD_LOCAL)
+#if (defined(XP_WIN) || defined(MACOSX_HAS_THREAD_LOCAL)) && !defined(__MINGW32__)
 #define MOZ_THREAD_LOCAL(TYPE) thread_local mozilla::detail::ThreadLocal<TYPE, mozilla::detail::ThreadLocalNativeStorage>
 #elif defined(HAVE_THREAD_TLS_KEYWORD)
 #define MOZ_THREAD_LOCAL(TYPE) __thread mozilla::detail::ThreadLocal<TYPE, mozilla::detail::ThreadLocalNativeStorage>
 #else
 #define MOZ_THREAD_LOCAL(TYPE) mozilla::detail::ThreadLocal<TYPE, mozilla::detail::ThreadLocalKeyStorage>
 #endif
 
 } // namespace detail