diff --git a/xfr.go b/xfr.go
index f30beb95..bd440476 100644
--- a/xfr.go
+++ b/xfr.go
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build !appengine
+
 package dns
 
 // New Transfer