diff --git a/lib/libc/string/strcat.3 b/lib/libc/string/strcat.3
index 316b6b9aad63..506cd89c749c 100644
--- a/lib/libc/string/strcat.3
+++ b/lib/libc/string/strcat.3
@@ -47,9 +47,9 @@
 .Sh SYNOPSIS
 .In string.h
 .Ft char *
-.Fn strcat "char *s" "const char *append"
+.Fn strcat "char *restrict s" "const char *restrict append"
 .Ft char *
-.Fn strncat "char *s" "const char *append" "size_t count"
+.Fn strncat "char *restrict s" "const char *restrict append" "size_t count"
 .Sh DESCRIPTION
 The
 .Fn strcat
diff --git a/lib/libc/string/strcat.c b/lib/libc/string/strcat.c
index 2bfd7b726e63..f7654d6e1fd3 100644
--- a/lib/libc/string/strcat.c
+++ b/lib/libc/string/strcat.c
@@ -40,9 +40,7 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 
 char *
-strcat(s, append)
-	char *s;
-	const char *append;
+strcat(char *__restrict s, const char *__restrict append)
 {
 	char *save = s;
 
diff --git a/lib/libc/string/strcpy.3 b/lib/libc/string/strcpy.3
index ae399ab5569d..9a6172742471 100644
--- a/lib/libc/string/strcpy.3
+++ b/lib/libc/string/strcpy.3
@@ -47,9 +47,9 @@
 .Sh SYNOPSIS
 .In string.h
 .Ft char *
-.Fn strcpy "char *dst" "const char *src"
+.Fn strcpy "char *restrict dst" "const char *restrict src"
 .Ft char *
-.Fn strncpy "char *dst" "const char *src" "size_t len"
+.Fn strncpy "char *restrict dst" "const char *restrict src" "size_t len"
 .Sh DESCRIPTION
 The
 .Fn strcpy
diff --git a/lib/libc/string/strcpy.c b/lib/libc/string/strcpy.c
index 590a5fbfe61c..56bc1a87561b 100644
--- a/lib/libc/string/strcpy.c
+++ b/lib/libc/string/strcpy.c
@@ -40,9 +40,7 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 
 char *
-strcpy(to, from)
-	char *to;
-	const char *from;
+strcpy(char *__restrict to, const char *__restrict from)
 {
 	char *save = to;
 
diff --git a/lib/libc/string/strncat.c b/lib/libc/string/strncat.c
index cc5ab671743c..2cf8f8300bf5 100644
--- a/lib/libc/string/strncat.c
+++ b/lib/libc/string/strncat.c
@@ -47,10 +47,7 @@ __FBSDID("$FreeBSD$");
  * are written at dst (at most n+1 bytes being appended).  Return dst.
  */
 char *
-strncat(dst, src, n)
-	char *dst;
-	const char *src;
-	size_t n;
+strncat(char *__restrict dst, const char *__restrict src, size_t n)
 {
 	if (n != 0) {
 		char *d = dst;
diff --git a/lib/libc/string/strncpy.c b/lib/libc/string/strncpy.c
index 771ebe60f091..90f848242766 100644
--- a/lib/libc/string/strncpy.c
+++ b/lib/libc/string/strncpy.c
@@ -47,10 +47,7 @@ __FBSDID("$FreeBSD$");
  * Return dst.
  */
 char *
-strncpy(dst, src, n)
-	char *dst;
-	const char *src;
-	size_t n;
+strncpy(char *__restrict dst, const char *__restrict src, size_t n)
 {
 	if (n != 0) {
 		char *d = dst;