diff --git a/stand/libsa/dosfs.c b/stand/libsa/dosfs.c
index 68762842eaee..2d6029be837e 100644
--- a/stand/libsa/dosfs.c
+++ b/stand/libsa/dosfs.c
@@ -403,7 +403,7 @@ dos_stat(struct open_file *fd, struct stat *sb)
 }
 
 static int
-dos_checksum(char *name, char *ext)
+dos_checksum(unsigned char *name, unsigned char *ext)
 {
     int x, i;
     char buf[11];