diff --git a/libkern/strstr.c b/libkern/strstr.c
index 74592a3..022e565 100644
--- a/libkern/strstr.c
+++ b/libkern/strstr.c
@@ -1,3 +1,5 @@
+/*	$NetBSD: strstr.c,v 1.1 2005/12/20 19:28:52 christos Exp $	*/
+
 /*-
  * Copyright (c) 1990, 1993
  *	The Regents of the University of California.  All rights reserved.
@@ -13,11 +15,7 @@
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
+ * 3. Neither the name of the University nor the names of its contributors
  *    may be used to endorse or promote products derived from this software
  *    without specific prior written permission.
  *
@@ -50,11 +48,17 @@
  * Find the first occurrence of find in s.
  */
 char *
-strstr(const char *s, const char *find)
+strstr(s, find)
+	const char *s, *find;
 {
 	char c, sc;
 	size_t len;
 
+	if (BUILTIN_EXPECT(!s, 0))
+		return NULL;
+	if (BUILTIN_EXPECT(!find, 0))
+		return NULL;
+
 	if ((c = *find++) != 0) {
 		len = strlen(find);
 		do {