diff --git a/crypto/multisig/threshold_multisig.go b/crypto/multisig/threshold_multisig.go
index 4ea69050..adc5fd12 100644
--- a/crypto/multisig/threshold_multisig.go
+++ b/crypto/multisig/threshold_multisig.go
@@ -34,7 +34,7 @@ func (pk *ThresholdMultiSignaturePubKey) VerifyBytes(msg []byte, marshalledSig [
 		return false
 	}
 	size := sig.BitArray.Size()
-	if len(sig.Sigs) < int(pk.K) || len(pk.Pubkeys) != size {
+	if len(sig.Sigs) < int(pk.K) || len(pk.Pubkeys) != size || sig.BitArray.NumOfTrueBitsBefore(size) < int(pk.K) {
 		return false
 	}
 	// index in the list of signatures which we are concerned with.
diff --git a/crypto/multisig/threshold_multisig_test.go b/crypto/multisig/threshold_multisig_test.go
index c3c4263f..cbd447a2 100644
--- a/crypto/multisig/threshold_multisig_test.go
+++ b/crypto/multisig/threshold_multisig_test.go
@@ -19,9 +19,9 @@ func TestThresholdMultisig(t *testing.T) {
 	require.False(t, multisigKey.VerifyBytes(msg, multisignature.Marshal()))
 	multisignature.AddSignatureFromPubkey(sigs[0], pubkeys[0], pubkeys)
 	require.False(t, multisigKey.VerifyBytes(msg, multisignature.Marshal()))
-	// Make sure adding the same signature twice doesn't make the signature pass
+	// Make sure adding the same signature twice doesn't increase number of signatures
 	multisignature.AddSignatureFromPubkey(sigs[0], pubkeys[0], pubkeys)
-	require.False(t, multisigKey.VerifyBytes(msg, multisignature.Marshal()))
+	require.Equal(t, 1, len(multisignature.Sigs))
 
 	// Adding two signatures should make it pass, as k = 2
 	multisignature.AddSignatureFromPubkey(sigs[3], pubkeys[3], pubkeys)
@@ -39,6 +39,18 @@ func TestThresholdMultisig(t *testing.T) {
 	require.False(t, multisigKey.VerifyBytes(msg, multisignature.Marshal()))
 }
 
+func TestThresholdMultisigDuplicateSignatures(t *testing.T) {
+	msg := []byte{1, 2, 3, 4, 5}
+	pubkeys, sigs := generatePubKeysAndSignatures(5, msg)
+	multisigKey := NewThresholdMultiSignaturePubKey(2, pubkeys)
+	multisignature := NewMultisig(5)
+	require.False(t, multisigKey.VerifyBytes(msg, multisignature.Marshal()))
+	multisignature.AddSignatureFromPubkey(sigs[0], pubkeys[0], pubkeys)
+	// Add second signature manually
+	multisignature.Sigs = append(multisignature.Sigs, sigs[0])
+	require.False(t, multisigKey.VerifyBytes(msg, multisignature.Marshal()))
+}
+
 func TestMultiSigPubkeyEquality(t *testing.T) {
 	msg := []byte{1, 2, 3, 4}
 	pubkeys, _ := generatePubKeysAndSignatures(5, msg)