diff --git a/mkfs.c b/mkfs.c
index 957460a..0a10754 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -11,7 +11,9 @@
 #include "stat.h"
 #include "param.h"
 
+#ifndef static_assert
 #define static_assert(a, b) do { switch (0) case 0: case (a): ; } while (0)
+#endif
 
 #define NINODES 200