diff --git a/whisper/whisperv5/filter.go b/whisper/whisperv5/filter.go
index b5e893e0ff..6568c0aea4 100644
--- a/whisper/whisperv5/filter.go
+++ b/whisper/whisperv5/filter.go
@@ -220,6 +220,10 @@ func matchSingleTopic(topic TopicType, bt []byte) bool {
 		bt = bt[:4]
 	}
 
+	if len(bt) < 4 {
+		return false
+	}
+
 	for j, b := range bt {
 		if topic[j] != b {
 			return false
diff --git a/whisper/whisperv6/filter.go b/whisper/whisperv6/filter.go
index 2f52dd6b98..d1e2c447f8 100644
--- a/whisper/whisperv6/filter.go
+++ b/whisper/whisperv6/filter.go
@@ -225,6 +225,10 @@ func matchSingleTopic(topic TopicType, bt []byte) bool {
 		bt = bt[:4]
 	}
 
+	if len(bt) < 4 {
+		return false
+	}
+
 	for j, b := range bt {
 		if topic[j] != b {
 			return false