diff --git a/utfutf.c b/utfutf.c
index 13c8502..ec49231 100644
--- a/utfutf.c
+++ b/utfutf.c
@@ -7,24 +7,25 @@
  * or modification of this software and in all copies of the supporting
  * documentation for such software.
  * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
- * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
- * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
+ * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY
+ * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
  */
 #include <stdarg.h>
 #include <string.h>
-#include "plan9.h"
 #include "utf.h"
+#include "utfdef.h"
 
 
 /*
  * Return pointer to first occurrence of s2 in s1,
  * 0 if none
  */
+const
 char*
-utfutf(char *s1, char *s2)
+utfutf(const char *s1, const char *s2)
 {
-	char *p;
+	const char *p;
 	long f, n1, n2;
 	Rune r;
 
@@ -34,7 +35,7 @@
 		return strstr(s1, s2);
 
 	n2 = strlen(s2);
-	for(p=s1; p=utfrune(p, f); p+=n1)
+	for(p=s1; (p=utfrune(p, f)) != 0; p+=n1)
 		if(strncmp(p, s2, n2) == 0)
 			return p;
 	return 0;