diff --git a/types/evidence.go b/types/evidence.go
index d6b408119..94bab1a38 100644
--- a/types/evidence.go
+++ b/types/evidence.go
@@ -149,10 +149,10 @@ func (dve *DuplicateVoteEvidence) Verify(chainID string) error {
 
 	// Signatures must be valid
 	if !dve.PubKey.VerifyBytes(SignBytes(chainID, dve.VoteA), dve.VoteA.Signature) {
-		return ErrVoteInvalidSignature
+		return fmt.Errorf("DuplicateVoteEvidence Error verifying VoteA: %v", ErrVoteInvalidSignature)
 	}
 	if !dve.PubKey.VerifyBytes(SignBytes(chainID, dve.VoteB), dve.VoteB.Signature) {
-		return ErrVoteInvalidSignature
+		return fmt.Errorf("DuplicateVoteEvidence Error verifying VoteB: %v", ErrVoteInvalidSignature)
 	}
 
 	return nil
diff --git a/types/vote.go b/types/vote.go
index 3136e4bb8..4397152c7 100644
--- a/types/vote.go
+++ b/types/vote.go
@@ -14,12 +14,13 @@ import (
 )
 
 var (
-	ErrVoteUnexpectedStep          = errors.New("Unexpected step")
-	ErrVoteInvalidValidatorIndex   = errors.New("Invalid validator index")
-	ErrVoteInvalidValidatorAddress = errors.New("Invalid validator address")
-	ErrVoteInvalidSignature        = errors.New("Invalid signature")
-	ErrVoteInvalidBlockHash        = errors.New("Invalid block hash")
-	ErrVoteNil                     = errors.New("Nil vote")
+	ErrVoteUnexpectedStep            = errors.New("Unexpected step")
+	ErrVoteInvalidValidatorIndex     = errors.New("Invalid validator index")
+	ErrVoteInvalidValidatorAddress   = errors.New("Invalid validator address")
+	ErrVoteInvalidSignature          = errors.New("Invalid signature")
+	ErrVoteInvalidBlockHash          = errors.New("Invalid block hash")
+	ErrVoteNonDeterministicSignature = errors.New("Non-deterministic signature")
+	ErrVoteNil                       = errors.New("Nil vote")
 )
 
 type ErrVoteConflictingVotes struct {
diff --git a/types/vote_set.go b/types/vote_set.go
index 3f8a96e3a..34f989567 100644
--- a/types/vote_set.go
+++ b/types/vote_set.go
@@ -6,6 +6,8 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/pkg/errors"
+
 	cmn "github.com/tendermint/tmlibs/common"
 )
 
@@ -145,27 +147,32 @@ func (voteSet *VoteSet) addVote(vote *Vote) (added bool, err error) {
 
 	// Ensure that validator index was set
 	if valIndex < 0 {
-		return false, ErrVoteInvalidValidatorIndex
+		return false, errors.Wrap(ErrVoteInvalidValidatorIndex, "Index < 0")
 	} else if len(valAddr) == 0 {
-		return false, ErrVoteInvalidValidatorAddress
+		return false, errors.Wrap(ErrVoteInvalidValidatorAddress, "Empty address")
 	}
 
 	// Make sure the step matches.
 	if (vote.Height != voteSet.height) ||
 		(vote.Round != voteSet.round) ||
 		(vote.Type != voteSet.type_) {
-		return false, ErrVoteUnexpectedStep
+		return false, errors.Wrapf(ErrVoteUnexpectedStep, "Got %d/%d/%d, expected %d/%d/%d",
+			voteSet.height, voteSet.round, voteSet.type_,
+			vote.Height, vote.Round, vote.Type)
 	}
 
 	// Ensure that signer is a validator.
 	lookupAddr, val := voteSet.valSet.GetByIndex(valIndex)
 	if val == nil {
-		return false, ErrVoteInvalidValidatorIndex
+		return false, errors.Wrapf(ErrVoteInvalidValidatorIndex,
+			"Cannot find validator %d in valSet of size %d", valIndex, voteSet.valSet.Size())
 	}
 
 	// Ensure that the signer has the right address
 	if !bytes.Equal(valAddr, lookupAddr) {
-		return false, ErrVoteInvalidValidatorAddress
+		return false, errors.Wrapf(ErrVoteInvalidValidatorAddress,
+			"vote.ValidatorAddress (%X) does not match address (%X) for vote.ValidatorIndex (%d)",
+			valAddr, lookupAddr, valIndex)
 	}
 
 	// If we already know of this vote, return false.
@@ -173,13 +180,13 @@ func (voteSet *VoteSet) addVote(vote *Vote) (added bool, err error) {
 		if existing.Signature.Equals(vote.Signature) {
 			return false, nil // duplicate
 		} else {
-			return false, ErrVoteInvalidSignature // NOTE: assumes deterministic signatures
+			return false, errors.Wrapf(ErrVoteNonDeterministicSignature, "Existing vote: %v; New vote: %v", existing, vote)
 		}
 	}
 
 	// Check signature.
 	if err := vote.Verify(voteSet.chainID, val.PubKey); err != nil {
-		return false, err
+		return false, errors.Wrapf(err, "Failed to verify vote with ChainID %s and PubKey %s", voteSet.chainID, val.PubKey)
 	}
 
 	// Add vote and get conflicting vote if any