diff --git a/src/vkutil.h b/src/vkutil.h
index e3545051..2c7f9322 100644
--- a/src/vkutil.h
+++ b/src/vkutil.h
@@ -37,7 +37,7 @@
 #include <sys/types.h>
 
 /* Static assert macro for C99. */
-#define vk_static_assert(cond) extern char vk_static_assert[sizeof(char[1 - 2 * !(cond)])]
+#define vk_static_assert(cond) extern char vk_static_assert[sizeof(char[(cond) ? 1 : -1])]
 
 /*
  * Wrapper to workaround well known, safe, implicit type conversion when