diff --git a/openflow15/group.go b/openflow15/group.go
index d312364..1deb15d 100644
--- a/openflow15/group.go
+++ b/openflow15/group.go
@@ -126,7 +126,6 @@ func (g *GroupMod) MarshalBinary() (data []byte, err error) {
 			return
 		}
 		data = append(data, bytes...)
-		g.BucketArrayLen += bkt.Len()
 	}
 
 	for _, p := range g.Properties {
diff --git a/openflow15_test.go b/openflow15_test.go
index 4805d33..e7e5622 100644
--- a/openflow15_test.go
+++ b/openflow15_test.go
@@ -87,6 +87,13 @@ func validateOpenflowMessage(m util.Message, n util.Message) error {
 		return err
 	}
 
+	// check that marshalling doesn't change internal state
+	x2, err := n.MarshalBinary()
+	if err != nil {
+		fmt.Printf("Second MarshalBinary failed with error code: %v", err)
+		return err
+	}
+
 	// Debug block
 	if false { // set to true if you want to write second pass message to be
 		// written to the pcap file as well.
@@ -112,6 +119,12 @@ func validateOpenflowMessage(m util.Message, n util.Message) error {
 		myErr.s = "MarshalBinary bytes don't match with original"
 		return myErr
 	}
+
+	if bytes.Equal(x, x2) == false {
+		var myErr MyError
+		myErr.s = "Results of first and second run of MarshalBinary are different"
+		return myErr
+	}
 	return nil
 }