diff --git a/src/net/mockserver_test.go b/src/net/mockserver_test.go
index dd6f4df3b9..38b317af7d 100644
--- a/src/net/mockserver_test.go
+++ b/src/net/mockserver_test.go
@@ -30,10 +30,20 @@ func testUnixAddr() string {
 
 func newLocalListener(network string) (Listener, error) {
 	switch network {
-	case "tcp", "tcp4", "tcp6":
+	case "tcp":
+		if supportsIPv4 {
+			if ln, err := Listen("tcp4", "127.0.0.1:0"); err == nil {
+				return ln, nil
+			}
+		}
+		if supportsIPv6 {
+			return Listen("tcp6", "[::1]:0")
+		}
+	case "tcp4":
 		if supportsIPv4 {
 			return Listen("tcp4", "127.0.0.1:0")
 		}
+	case "tcp6":
 		if supportsIPv6 {
 			return Listen("tcp6", "[::1]:0")
 		}