diff --git a/trie/trie.h b/trie/trie.h
index 1a7868e..154aafd 100644
--- a/trie/trie.h
+++ b/trie/trie.h
@@ -13,6 +13,7 @@ union ipv6 {
 
 #define VALID_RULE 1
 #define INVALID_RULE 0
+#define RULE_NOT_FOUND -1
 
 struct trie_node {
     struct trie_node*   _l;