--- a/include/firewalk.h
+++ b/include/firewalk.h
@@ -280,7 +280,7 @@
 /* dump usage */
 void
 usage(
-    u_char *                        /* argv[0] */
+    char *                        /* argv[0] */
     );
 
 #endif /* _FIREWALK_H */
--- a/src/main.c
+++ b/src/main.c
@@ -171,7 +171,7 @@
 }
 
 void
-usage(u_char *argv0)
+usage(char *argv0)
 {
     fprintf(stderr, "Usage : %s [options] target_gateway metric\n"
         "\t\t   [-d %d - %d] destination port to use (ramping phase)\n"