diff --git a/lib/kafs/kafs.h b/lib/kafs/kafs.h
index 02ab9e064..5cf18de4f 100644
--- a/lib/kafs/kafs.h
+++ b/lib/kafs/kafs.h
@@ -101,9 +101,15 @@ struct ClearToken {
   int32_t EndTimestamp;
 };
 
+#ifdef __STDC__
 #ifndef __P
 #define __P(x) x
 #endif
+#else
+#ifndef __P
+#define __P(x) ()
+#endif
+#endif
 
 /* Use k_hasafs() to probe if the machine supports AFS syscalls.
    The other functions will generate a SIGSYS if AFS is not supported */