diff --git a/src/croc/croc.go b/src/croc/croc.go
index ab6bfa7..9095934 100644
--- a/src/croc/croc.go
+++ b/src/croc/croc.go
@@ -778,7 +778,7 @@ func (c *Client) Receive() (err error) {
 					continue
 				}
 
-				serverTry := fmt.Sprintf("%s:%s", ip, port)
+				serverTry := net.JoinHostPort(ip, port)
 				conn, banner2, externalIP, errConn := tcp.ConnectToTCPServer(serverTry, c.Options.RelayPassword, c.Options.SharedSecret[:3], 500*time.Millisecond)
 				if errConn != nil {
 					log.Debug(errConn)
diff --git a/src/models/constants.go b/src/models/constants.go
index 8fdb9c0..d2edac1 100644
--- a/src/models/constants.go
+++ b/src/models/constants.go
@@ -79,15 +79,16 @@ func init() {
 		}
 	}
 	var err error
-	DEFAULT_RELAY, err = lookup(DEFAULT_RELAY)
+	var addr string
+	addr, err = lookup(DEFAULT_RELAY)
 	if err == nil {
-		DEFAULT_RELAY += ":" + DEFAULT_PORT
+		DEFAULT_RELAY = net.JoinHostPort(addr, DEFAULT_PORT)
 	} else {
 		DEFAULT_RELAY = ""
 	}
-	DEFAULT_RELAY6, err = lookup(DEFAULT_RELAY6)
+	addr, err = lookup(DEFAULT_RELAY6)
 	if err == nil {
-		DEFAULT_RELAY6 = "[" + DEFAULT_RELAY6 + "]:" + DEFAULT_PORT
+		DEFAULT_RELAY6 = net.JoinHostPort(addr, DEFAULT_PORT)
 	} else {
 		DEFAULT_RELAY6 = ""
 	}