diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index b0ec498a18d9d86eca840aced3f1580744ef8b71..52c7a151e298fbcd2a467697e7e448720beca175 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -4,6 +4,10 @@
 
 #include <asm/unistd.h>
 
+/*  we can't #include <linux/syscalls.h> here,
+    but tell gcc to not warn with -Wmissing-prototypes  */
+asmlinkage long sys_ni_syscall(void);
+
 /*
  * Non-implemented system calls get redirected here.
  */