diff --git a/upb/port_def.inc b/upb/port_def.inc
index 4cd082589a..2cd1bb6985 100644
--- a/upb/port_def.inc
+++ b/upb/port_def.inc
@@ -21,12 +21,10 @@
 * This file is private and must not be included by users!
 */
 
-#if !(__STDC_VERSION__ >= 199901L || __cplusplus >= 201103L)
-#error upb requires C99 or C++11
-#endif
-
-#if (defined(_MSC_VER) && _MSC_VER < 1900)
-#error upb requires MSVC >= 2015.
+#if !((defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) || \
+      (defined(__cplusplus) && __cplusplus >= 201103L) ||           \
+      (defined(_MSC_VER) && _MSC_VER >= 1900))
+#error upb requires C99 or C++11 or MSVC >= 2015.
 #endif
 
 #include <stdint.h>