diff --git a/consensus/state.go b/consensus/state.go
index 2f9f07ec3..4785b3621 100644
--- a/consensus/state.go
+++ b/consensus/state.go
@@ -1338,10 +1338,7 @@ func (cs *ConsensusState) tryAddVote(vote *types.Vote, peerKey string) error {
 				cs.Logger.Error("Found conflicting vote from ourselves. Did you unsafe_reset a validator?", "height", vote.Height, "round", vote.Round, "type", vote.Type)
 				return err
 			}
-			cs.Logger.Error("Found conflicting vote. Recording evidence in the RoundState", "height", vote.Height, "round", vote.Round, "type", vote.Type, "valAddr", vote.ValidatorAddress, "valIndex", vote.ValidatorIndex)
-
-			// TODO: ensure we haven't seen this evidence already !
-			cs.Evidence = append(cs.Evidence, voteErr.DuplicateVoteEvidence)
+			cs.addEvidence(voteErr.DuplicateVoteEvidence)
 			return err
 		} else {
 			// Probably an invalid signature / Bad peer.
@@ -1353,6 +1350,16 @@ func (cs *ConsensusState) tryAddVote(vote *types.Vote, peerKey string) error {
 	return nil
 }
 
+func (cs *ConsensusState) addEvidence(ev types.Evidence) {
+	if cs.Evidence.Has(ev) {
+		return
+	}
+
+	cs.Logger.Error("Found conflicting vote. Recording evidence in the RoundState", "evidence", ev)
+
+	cs.Evidence = append(cs.Evidence, ev)
+}
+
 //-----------------------------------------------------------------------------
 
 func (cs *ConsensusState) addVote(vote *types.Vote, peerKey string) (added bool, err error) {
diff --git a/types/block.go b/types/block.go
index fa59c8420..b3e754427 100644
--- a/types/block.go
+++ b/types/block.go
@@ -86,7 +86,6 @@ func (b *Block) FillHeader() {
 // Hash computes and returns the block hash.
 // If the block is incomplete, block hash is nil for safety.
 func (b *Block) Hash() data.Bytes {
-	// fmt.Println(">>", b.Data)
 	if b == nil || b.Header == nil || b.Data == nil || b.LastCommit == nil {
 		return nil
 	}
diff --git a/types/evidence.go b/types/evidence.go
index 2756faf3b..d40c63ea2 100644
--- a/types/evidence.go
+++ b/types/evidence.go
@@ -30,6 +30,7 @@ type Evidence interface {
 	Address() []byte
 	Hash() []byte
 	Verify(chainID string) error
+	Equal(Evidence) bool
 
 	String() string
 }
@@ -61,6 +62,15 @@ func (evs Evidences) String() string {
 	return s
 }
 
+func (evs Evidences) Has(evidence Evidence) bool {
+	for _, ev := range evs {
+		if ev.Equal(evidence) {
+			return true
+		}
+	}
+	return false
+}
+
 //-------------------------------------------
 
 // DuplicateVoteEvidence contains evidence a validator signed two conflicting votes.
@@ -120,3 +130,13 @@ func (dve *DuplicateVoteEvidence) Verify(chainID string) error {
 
 	return nil
 }
+
+// Equal checks if two pieces of evidence are equal.
+func (dve *DuplicateVoteEvidence) Equal(ev Evidence) bool {
+	if _, ok := ev.(*DuplicateVoteEvidence); !ok {
+		return false
+	}
+
+	// just check their hashes
+	return bytes.Equal(merkle.SimpleHashFromBinary(dve), merkle.SimpleHashFromBinary(ev))
+}