diff --git a/whisper/whisperv6/api.go b/whisper/whisperv6/api.go
index 96e2b17e7c..74b8873d10 100644
--- a/whisper/whisperv6/api.go
+++ b/whisper/whisperv6/api.go
@@ -558,9 +558,10 @@ func (api *PublicWhisperAPI) NewMessageFilter(req Criteria) (string, error) {
 	}
 
 	if len(req.Topics) > 0 {
-		topics = make([][]byte, 0, len(req.Topics))
-		for _, topic := range req.Topics {
-			topics = append(topics, topic[:])
+		topics = make([][]byte, len(req.Topics))
+		for i, topic := range req.Topics {
+			topics = append(topics, make([]byte, 0, len(topic)))
+			copy(topics[i], topic[:])
 		}
 	}