diff --git a/xxd/xxd.c b/xxd/xxd.c
index 20f06ab..55e64fe 100644
--- a/xxd/xxd.c
+++ b/xxd/xxd.c
@@ -132,8 +132,8 @@ extern void perror __P((char *));
 # endif
 #endif
 
-extern long int strtol();
-extern long int ftell();
+extern long int strtol(const char *restrict, char **restrict, int);
+extern long int ftell(FILE *);
 
 char version[] = "xxd V1.10 27oct98 by Juergen Weigert";
 #ifdef WIN32