diff --git a/component/domain-trie/tire.go b/component/domain-trie/tire.go
index 26062fc2..f4e87ff5 100644
--- a/component/domain-trie/tire.go
+++ b/component/domain-trie/tire.go
@@ -22,7 +22,7 @@ type Trie struct {
 }
 
 func isValidDomain(domain string) bool {
-	return domain[0] != '.' && domain[len(domain)-1] != '.'
+	return domain != "" && domain[0] != '.' && domain[len(domain)-1] != '.'
 }
 
 // Insert adds a node to the trie.
diff --git a/component/domain-trie/trie_test.go b/component/domain-trie/trie_test.go
index 5303596b..228106cd 100644
--- a/component/domain-trie/trie_test.go
+++ b/component/domain-trie/trie_test.go
@@ -26,6 +26,10 @@ func TestTrie_Basic(t *testing.T) {
 	if !node.Data.(net.IP).Equal(localIP) {
 		t.Error("should equal 127.0.0.1")
 	}
+
+	if tree.Insert("", localIP) == nil {
+		t.Error("should return error")
+	}
 }
 
 func TestTrie_Wildcard(t *testing.T) {