diff --git a/whisper/whisperv5/api.go b/whisper/whisperv5/api.go
index 7fd76ee5b0..b4494d0d61 100644
--- a/whisper/whisperv5/api.go
+++ b/whisper/whisperv5/api.go
@@ -562,7 +562,7 @@ func (api *PublicWhisperAPI) NewMessageFilter(req Criteria) (string, error) {
 	}
 
 	if len(req.Topics) > 0 {
-		topics = make([][]byte, 0, 1)
+		topics = make([][]byte, 0, len(req.Topics))
 		for _, topic := range req.Topics {
 			topics = append(topics, topic[:])
 		}
diff --git a/whisper/whisperv5/filter.go b/whisper/whisperv5/filter.go
index 6568c0aea4..3190334ebb 100644
--- a/whisper/whisperv5/filter.go
+++ b/whisper/whisperv5/filter.go
@@ -216,11 +216,11 @@ func (f *Filter) MatchTopic(topic TopicType) bool {
 }
 
 func matchSingleTopic(topic TopicType, bt []byte) bool {
-	if len(bt) > 4 {
-		bt = bt[:4]
+	if len(bt) > TopicLength {
+		bt = bt[:TopicLength]
 	}
 
-	if len(bt) < 4 {
+	if len(bt) < TopicLength {
 		return false
 	}
 
diff --git a/whisper/whisperv5/filter_test.go b/whisper/whisperv5/filter_test.go
index 72568b94e6..26d09e1060 100644
--- a/whisper/whisperv5/filter_test.go
+++ b/whisper/whisperv5/filter_test.go
@@ -796,19 +796,48 @@ func TestVariableTopics(t *testing.T) {
 	}
 
 	for i := 0; i < 4; i++ {
-		arr := make([]byte, i+1, 4)
-		copy(arr, env.Topic[:i+1])
-
-		f.Topics[4] = arr
+		env.Topic = BytesToTopic(f.Topics[i])
 		match = f.MatchEnvelope(env)
 		if !match {
 			t.Fatalf("failed MatchEnvelope symmetric with seed %d, step %d.", seed, i)
 		}
 
-		f.Topics[4][i]++
+		f.Topics[i][1]++
 		match = f.MatchEnvelope(env)
 		if match {
 			t.Fatalf("MatchEnvelope symmetric with seed %d, step %d: false positive.", seed, i)
 		}
 	}
 }
+
+func TestMatchSingleTopic_ReturnTrue(t *testing.T) {
+	bt := []byte("test")
+	topic := BytesToTopic(bt)
+	if matchSingleTopic(topic, bt) == false {
+		t.FailNow()
+	}
+}
+
+func TestMatchSingleTopic_WithTail_ReturnTrue(t *testing.T) {
+	bt := []byte("test with tail")
+	topic := BytesToTopic([]byte("test"))
+	if matchSingleTopic(topic, bt) == false {
+		t.FailNow()
+	}
+}
+
+func TestMatchSingleTopic_NotEquals_ReturnFalse(t *testing.T) {
+	bt := []byte("tes")
+	topic := BytesToTopic(bt)
+	if matchSingleTopic(topic, bt) == true {
+		t.FailNow()
+	}
+}
+
+func TestMatchSingleTopic_InsufficientLength_ReturnFalse(t *testing.T) {
+	bt := []byte("test")
+	topic := BytesToTopic([]byte("not_equal"))
+	if matchSingleTopic(topic, bt) == true {
+		t.FailNow()
+	}
+}
diff --git a/whisper/whisperv6/api.go b/whisper/whisperv6/api.go
index 0cfab7cba2..a1dbeaa09e 100644
--- a/whisper/whisperv6/api.go
+++ b/whisper/whisperv6/api.go
@@ -562,7 +562,7 @@ func (api *PublicWhisperAPI) NewMessageFilter(req Criteria) (string, error) {
 	}
 
 	if len(req.Topics) > 0 {
-		topics = make([][]byte, 0, 1)
+		topics = make([][]byte, 0, len(req.Topics))
 		for _, topic := range req.Topics {
 			topics = append(topics, topic[:])
 		}
diff --git a/whisper/whisperv6/filter.go b/whisper/whisperv6/filter.go
index d1e2c447f8..a752c7ac9a 100644
--- a/whisper/whisperv6/filter.go
+++ b/whisper/whisperv6/filter.go
@@ -221,11 +221,11 @@ func (f *Filter) MatchTopic(topic TopicType) bool {
 }
 
 func matchSingleTopic(topic TopicType, bt []byte) bool {
-	if len(bt) > 4 {
-		bt = bt[:4]
+	if len(bt) > TopicLength {
+		bt = bt[:TopicLength]
 	}
 
-	if len(bt) < 4 {
+	if len(bt) < TopicLength {
 		return false
 	}
 
diff --git a/whisper/whisperv6/filter_test.go b/whisper/whisperv6/filter_test.go
index e2877b233c..c45a66c382 100644
--- a/whisper/whisperv6/filter_test.go
+++ b/whisper/whisperv6/filter_test.go
@@ -820,19 +820,48 @@ func TestVariableTopics(t *testing.T) {
 	}
 
 	for i := 0; i < 4; i++ {
-		arr := make([]byte, i+1, 4)
-		copy(arr, env.Topic[:i+1])
-
-		f.Topics[4] = arr
+		env.Topic = BytesToTopic(f.Topics[i])
 		match = f.MatchEnvelope(env)
 		if !match {
 			t.Fatalf("failed MatchEnvelope symmetric with seed %d, step %d.", seed, i)
 		}
 
-		f.Topics[4][i]++
+		f.Topics[i][1]++
 		match = f.MatchEnvelope(env)
 		if match {
 			t.Fatalf("MatchEnvelope symmetric with seed %d, step %d: false positive.", seed, i)
 		}
 	}
 }
+
+func TestMatchSingleTopic_ReturnTrue(t *testing.T) {
+	bt := []byte("test")
+	topic := BytesToTopic(bt)
+	if matchSingleTopic(topic, bt) == false {
+		t.FailNow()
+	}
+}
+
+func TestMatchSingleTopic_WithTail_ReturnTrue(t *testing.T) {
+	bt := []byte("test with tail")
+	topic := BytesToTopic([]byte("test"))
+	if matchSingleTopic(topic, bt) == false {
+		t.FailNow()
+	}
+}
+
+func TestMatchSingleTopic_NotEquals_ReturnFalse(t *testing.T) {
+	bt := []byte("tes")
+	topic := BytesToTopic(bt)
+	if matchSingleTopic(topic, bt) == true {
+		t.FailNow()
+	}
+}
+
+func TestMatchSingleTopic_InsufficientLength_ReturnFalse(t *testing.T) {
+	bt := []byte("test")
+	topic := BytesToTopic([]byte("not_equal"))
+	if matchSingleTopic(topic, bt) == true {
+		t.FailNow()
+	}
+}