diff --git a/include/msvcrt/stddef.h b/include/msvcrt/stddef.h
index 8d946e5aedf..b3fdaf0c052 100644
--- a/include/msvcrt/stddef.h
+++ b/include/msvcrt/stddef.h
@@ -20,7 +20,7 @@
 
 #include <corecrt.h>
 
-#ifdef __GNUC__
+#if defined(__GNUC__) || defined(__clang__)
 #define offsetof(s,m)       __builtin_offsetof(s,m)
 #elif defined(_WIN64)
 #define offsetof(s,m)       (size_t)((ptrdiff_t)&(((s*)NULL)->m))