diff --git a/include/os.h b/include/os.h
index 360bb793fc..8ef9094942 100644
--- a/include/os.h
+++ b/include/os.h
@@ -71,7 +71,7 @@ SOFTWARE.
 #endif
 
 #ifndef _X_ATTRIBUTE_VPRINTF
-# if defined(__GNUC__) && (__GNUC__ >= 2) && (!defined(__APPLE__)) && (!defined(__FreeBSD__))
+# if defined(__GNUC__) && (__GNUC__ >= 2) && !defined(__clang__)
 #  define _X_ATTRIBUTE_VPRINTF(fmt, firstarg) \
           __attribute__((__format__(gnu_printf, fmt, firstarg)))
 # else