diff --git a/include/string.h b/include/string.h
index 75e85580d21b..91007f130482 100644
--- a/include/string.h
+++ b/include/string.h
@@ -85,8 +85,8 @@ char	*strerror(int);
 int	 strerror_r(int, char *, size_t);
 #endif
 #if __BSD_VISIBLE
-size_t	 strlcat(char *, const char *, size_t);
-size_t	 strlcpy(char *, const char *, size_t);
+size_t	 strlcat(char * __restrict, const char * __restrict, size_t);
+size_t	 strlcpy(char * __restrict, const char * __restrict, size_t);
 #endif
 size_t	 strlen(const char *) __pure;
 #if __BSD_VISIBLE
diff --git a/lib/libc/string/strlcat.c b/lib/libc/string/strlcat.c
index feeac3bb11c6..2d13be77f131 100644
--- a/lib/libc/string/strlcat.c
+++ b/lib/libc/string/strlcat.c
@@ -30,7 +30,7 @@ __FBSDID("$FreeBSD$");
  * If retval >= siz, truncation occurred.
  */
 size_t
-strlcat(char *dst, const char *src, size_t siz)
+strlcat(char * __restrict dst, const char * __restrict src, size_t siz)
 {
 	char *d = dst;
 	const char *s = src;
diff --git a/lib/libc/string/strlcpy.3 b/lib/libc/string/strlcpy.3
index 88af06db1c61..aaef572aae2a 100644
--- a/lib/libc/string/strlcpy.3
+++ b/lib/libc/string/strlcpy.3
@@ -39,9 +39,9 @@
 .Sh SYNOPSIS
 .In string.h
 .Ft size_t
-.Fn strlcpy "char *dst" "const char *src" "size_t size"
+.Fn strlcpy "char * restrict dst" "const char * restrict src" "size_t size"
 .Ft size_t
-.Fn strlcat "char *dst" "const char *src" "size_t size"
+.Fn strlcat "char * restrict dst" "const char * restrict src" "size_t size"
 .Sh DESCRIPTION
 The
 .Fn strlcpy
diff --git a/lib/libc/string/strlcpy.c b/lib/libc/string/strlcpy.c
index 187bdb71f8ba..451b6df7980d 100644
--- a/lib/libc/string/strlcpy.c
+++ b/lib/libc/string/strlcpy.c
@@ -28,7 +28,7 @@ __FBSDID("$FreeBSD$");
  * Returns strlen(src); if retval >= siz, truncation occurred.
  */
 size_t
-strlcpy(char *dst, const char *src, size_t siz)
+strlcpy(char * __restrict dst, const char * __restrict src, size_t siz)
 {
 	char *d = dst;
 	const char *s = src;