diff --git a/default.go b/default.go
index 616d639..52d4077 100644
--- a/default.go
+++ b/default.go
@@ -58,6 +58,10 @@ func (api *LinkInfoApi) DefaultLinkHandler(link string) (*LinkInfo, error) {
 		return nil, err
 	}
 
+	if u.Scheme != "http" && u.Scheme != "https" {
+		return nil, errors.New("unsupported scheme")
+	}
+
 	if u.Host == "localhost" {
 		return nil, errors.New("url is localhost")
 	} else if ip := net.ParseIP(u.Host); ip != nil && isPrivateIP(ip) {