diff --git a/clay.h b/clay.h
index 1c91888e..0b724dc0 100644
--- a/clay.h
+++ b/clay.h
@@ -28,7 +28,7 @@
 #define CLAY_WASM_EXPORT(null)
 #endif
 
-#ifdef MSC_VER
+#ifdef _MSC_VER
 #define CLAY_PACKED_ENUM
 #else
 #define CLAY_PACKED_ENUM __attribute__((__packed__))