diff --git a/arch/sh/include/asm/uaccess_64.h b/arch/sh/include/asm/uaccess_64.h
index 81b3d515fcb36920938de61b13412a0d75e95fe4..5580fd471003e156b843df49f3eec236471e7335 100644
--- a/arch/sh/include/asm/uaccess_64.h
+++ b/arch/sh/include/asm/uaccess_64.h
@@ -76,4 +76,6 @@ extern long __put_user_asm_l(void *, long);
 extern long __put_user_asm_q(void *, long);
 extern void __put_user_unknown(void);
 
+extern long __strnlen_user(const char *__s, long __n);
+
 #endif /* __ASM_SH_UACCESS_64_H */