diff --git a/src/runtime/SYSTEM.h b/src/runtime/SYSTEM.h
index 3f3b6133..d9778393 100644
--- a/src/runtime/SYSTEM.h
+++ b/src/runtime/SYSTEM.h
@@ -26,7 +26,7 @@
 #define _SIZE_T_DEFINED_ // For OpenBSD
 
 void *memcpy(void *dest, const void *source, size_t size);
-#if defined _WIN32
+#if defined _MSC_VER
 #define alloca _alloca
 #endif
 void *alloca(size_t size);