diff --git a/src/mapi/u_thread.h b/src/mapi/u_thread.h
index 75fbec61dac..ba5d98ea902 100644
--- a/src/mapi/u_thread.h
+++ b/src/mapi/u_thread.h
@@ -92,7 +92,7 @@ typedef mtx_t u_mutex;
 static INLINE unsigned long
 u_thread_self(void)
 {
-   return (unsigned long) thrd_current();
+   return (unsigned long) (uintptr_t) thrd_current();
 }