diff --git a/include/common.h b/include/common.h
index d8c912d..893af5c 100644
--- a/include/common.h
+++ b/include/common.h
@@ -648,7 +648,7 @@ int	sprintf(char * buf, const char *fmt, ...)
 int	vsprintf(char *buf, const char *fmt, va_list args);
 
 /* lib/strmhz.c */
-char *	strmhz(char *buf, long hz);
+char *	strmhz(char *buf, unsigned long hz);
 
 /* lib/crc32.c */
 #include <u-boot/crc.h>
diff --git a/lib/strmhz.c b/lib/strmhz.c
index d6da1d1..89f2263 100644
--- a/lib/strmhz.c
+++ b/lib/strmhz.c
@@ -22,7 +22,7 @@
  */
 #include <common.h>
 
-char *strmhz (char *buf, long hz)
+char *strmhz (char *buf, unsigned long hz)
 {
 	long l, n;
 	long m;