diff --git a/internal/c/os.h b/internal/c/os.h
index d1d044aa2..72c0bf027 100644
--- a/internal/c/os.h
+++ b/internal/c/os.h
@@ -27,7 +27,7 @@
  #endif
 #endif
 
-#if _WIN64 || __x86_64__ || __ppc64__ || QB64_MACOSX
+#if defined(_WIN64) || defined(__x86_64__) || defined(__ppc64__) || defined(QB64_MACOSX)
  #define QB64_64
 #else
  #define QB64_32