diff --git a/lib/vty.c b/lib/vty.c
index 750f885..d623b85 100644
--- a/lib/vty.c
+++ b/lib/vty.c
@@ -870,7 +870,7 @@
 
   /* In case of 'help \t'. */
   if (isspace ((int) vty->buf[vty->length - 1]))
-    vector_set (vline, '\0');
+    vector_set (vline, NULL);
 
   matched = cmd_complete_command (vline, vty, &ret);
   
@@ -985,11 +985,11 @@
   if (vline == NULL)
     {
       vline = vector_init (1);
-      vector_set (vline, '\0');
+      vector_set (vline, NULL);
     }
   else 
     if (isspace ((int) vty->buf[vty->length - 1]))
-      vector_set (vline, '\0');
+      vector_set (vline, NULL);
 
   describe = cmd_describe_command (vline, vty, &ret);