diff --git a/x/observer/keeper/params_test.go b/x/observer/keeper/params_test.go
index c487ea0f73..149de0e583 100644
--- a/x/observer/keeper/params_test.go
+++ b/x/observer/keeper/params_test.go
@@ -1,4 +1,4 @@
-package keeper
+package keeper_test
 
 import (
 	"fmt"
@@ -9,11 +9,13 @@ import (
 	"github.com/tendermint/tendermint/crypto"
 
 	"github.com/stretchr/testify/require"
+	testutilkeeper "github.com/zeta-chain/zetacore/testutil/keeper"
+	"github.com/zeta-chain/zetacore/x/observer/keeper"
 	"github.com/zeta-chain/zetacore/x/observer/types"
 )
 
 func TestGetParams(t *testing.T) {
-	k, ctx := SetupKeeper(t)
+	k, ctx := keeper.SetupKeeper(t)
 	params := types.DefaultParams()
 
 	k.SetParams(ctx, params)
@@ -22,7 +24,7 @@ func TestGetParams(t *testing.T) {
 }
 
 func TestGenerateAddress(t *testing.T) {
-	types.SetConfig(false)
+	testutilkeeper.SetConfig(false)
 	addr := sdk.AccAddress(crypto.AddressHash([]byte("Output1" + strconv.Itoa(1))))
 	addrString := addr.String()
 	fmt.Println(addrString)
diff --git a/x/observer/types/ballot.go b/x/observer/types/ballot.go
index 10f21119d1..b9619d16ff 100644
--- a/x/observer/types/ballot.go
+++ b/x/observer/types/ballot.go
@@ -14,12 +14,18 @@ func (m Ballot) AddVote(address string, vote VoteType) (Ballot, error) {
 	// `index` is the index of the `address` in the `VoterList`
 	// `index` is used to set the vote in the `Votes` array
 	index := m.GetVoterIndex(address)
+	if index == -1 {
+		return m, errors.Wrap(ErrUnableToAddVote, fmt.Sprintf("Voter %s not in voter list", address))
+	}
 	m.Votes[index] = vote
 	return m, nil
 }
 
 func (m Ballot) HasVoted(address string) bool {
 	index := m.GetVoterIndex(address)
+	if index == -1 {
+		return false
+	}
 	return m.Votes[index] != VoteType_NotYetVoted
 }
 
diff --git a/x/observer/types/ballot_test.go b/x/observer/types/ballot_test.go
index 2bd6441c48..322affd728 100644
--- a/x/observer/types/ballot_test.go
+++ b/x/observer/types/ballot_test.go
@@ -21,6 +21,7 @@ func TestBallot_AddVote(t *testing.T) {
 		finalVotes  []VoteType
 		finalStatus BallotStatus
 		isFinalized bool
+		wantErr     bool
 	}{
 		{
 			name:      "All success",
@@ -188,6 +189,18 @@ func TestBallot_AddVote(t *testing.T) {
 			finalStatus: BallotStatus_BallotInProgress,
 			isFinalized: false,
 		},
+		{
+			name:      "Voter not in voter list",
+			threshold: sdk.MustNewDecFromStr("0.66"),
+			voterList: []string{},
+			votes: []votes{
+				{"Observer5", VoteType_SuccessObservation},
+			},
+			wantErr:     true,
+			finalVotes:  []VoteType{},
+			finalStatus: BallotStatus_BallotInProgress,
+			isFinalized: false,
+		},
 	}
 	for _, test := range tt {
 		test := test
@@ -202,7 +215,11 @@ func TestBallot_AddVote(t *testing.T) {
 				BallotStatus:     BallotStatus_BallotInProgress,
 			}
 			for _, vote := range test.votes {
-				ballot, _ = ballot.AddVote(vote.address, vote.vote)
+				b, err := ballot.AddVote(vote.address, vote.vote)
+				if test.wantErr {
+					require.Error(t, err)
+				}
+				ballot = b
 			}
 
 			finalBallot, isFinalized := ballot.IsFinalizingVote()
diff --git a/x/observer/types/test_data.go b/x/observer/types/test_data.go
deleted file mode 100644
index 3a43ca4306..0000000000
--- a/x/observer/types/test_data.go
+++ /dev/null
@@ -1,27 +0,0 @@
-package types
-
-import (
-	sdk "github.com/cosmos/cosmos-sdk/types"
-)
-
-const (
-	AccountAddressPrefix = "zeta"
-)
-
-var (
-	AccountPubKeyPrefix    = AccountAddressPrefix + "pub"
-	ValidatorAddressPrefix = AccountAddressPrefix + "valoper"
-	ValidatorPubKeyPrefix  = AccountAddressPrefix + "valoperpub"
-	ConsNodeAddressPrefix  = AccountAddressPrefix + "valcons"
-	ConsNodePubKeyPrefix   = AccountAddressPrefix + "valconspub"
-)
-
-func SetConfig(seal bool) {
-	config := sdk.GetConfig()
-	config.SetBech32PrefixForAccount(AccountAddressPrefix, AccountPubKeyPrefix)
-	config.SetBech32PrefixForValidator(ValidatorAddressPrefix, ValidatorPubKeyPrefix)
-	config.SetBech32PrefixForConsensusNode(ConsNodeAddressPrefix, ConsNodePubKeyPrefix)
-	if seal {
-		config.Seal()
-	}
-}