diff --git a/app/app.go b/app/app.go
index 0a6278bc..9f01e57f 100644
--- a/app/app.go
+++ b/app/app.go
@@ -164,9 +164,11 @@ func NewTerraApp(
 
 	// option for mempool
 	baseAppOptions = append(baseAppOptions, func(app *baseapp.BaseApp) {
-		mempool := appmempool.NewFifoMempool()
+		var mempool *appmempool.FifoMempool
 		if maxTxs := cast.ToInt(appOpts.Get(server.FlagMempoolMaxTxs)); maxTxs >= 0 {
 			mempool = appmempool.NewFifoMempool(appmempool.FifoMaxTxOpt(maxTxs))
+		} else {
+			mempool = appmempool.NewFifoMempool()
 		}
 		handler := baseapp.NewDefaultProposalHandler(mempool, app)
 		app.SetMempool(mempool)
diff --git a/app/helper/helper.go b/app/helper/helper.go
new file mode 100644
index 00000000..b445d07d
--- /dev/null
+++ b/app/helper/helper.go
@@ -0,0 +1,24 @@
+package helper
+
+import (
+	oracleexported "github.com/classic-terra/core/v3/x/oracle/exported"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+func IsOracleTx(msgs []sdk.Msg) bool {
+	if len(msgs) == 0 {
+		return false
+	}
+	for _, msg := range msgs {
+		switch msg.(type) {
+		case *oracleexported.MsgAggregateExchangeRatePrevote:
+			continue
+		case *oracleexported.MsgAggregateExchangeRateVote:
+			continue
+		default:
+			return false
+		}
+	}
+
+	return true
+}
diff --git a/app/mempool/mempool_fifo.go b/app/mempool/mempool_fifo.go
index 4d9d7ea9..20556a1a 100644
--- a/app/mempool/mempool_fifo.go
+++ b/app/mempool/mempool_fifo.go
@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"sync"
 
-	"github.com/classic-terra/core/v3/custom/auth/ante"
+	"github.com/classic-terra/core/v3/app/helper"
 	"github.com/cometbft/cometbft/libs/clist"
 	cmtsync "github.com/cometbft/cometbft/libs/sync"
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -81,7 +81,7 @@ func (mp *FifoMempool) Insert(_ context.Context, tx sdk.Tx) error {
 		return err
 	}
 	// Add to appropriate queue based on transaction type
-	if ante.IsOracleTx(tx.GetMsgs()) {
+	if helper.IsOracleTx(tx.GetMsgs()) {
 		e := mp.txsOracle.PushBack(tx)
 		mp.txsMapOracle.Store(txKey, e)
 	} else {
@@ -166,7 +166,7 @@ func (mp *FifoMempool) Remove(tx sdk.Tx) error {
 		return err
 	}
 
-	isOracle := ante.IsOracleTx(tx.GetMsgs())
+	isOracle := helper.IsOracleTx(tx.GetMsgs())
 	if isOracle {
 		if elem, ok := mp.txsMapOracle.LoadAndDelete(txKey); ok {
 			mp.txsOracle.Remove(elem.(*clist.CElement))
diff --git a/app/mempool/mempool_fifo_test.go b/app/mempool/mempool_fifo_test.go
index a0363743..8f1f009a 100644
--- a/app/mempool/mempool_fifo_test.go
+++ b/app/mempool/mempool_fifo_test.go
@@ -8,7 +8,7 @@ import (
 
 	stakingtypes "github.com/cosmos/cosmos-sdk/x/staking/types"
 
-	"github.com/classic-terra/core/v3/custom/auth/ante"
+	"github.com/classic-terra/core/v3/app/helper"
 	oracleexported "github.com/classic-terra/core/v3/x/oracle/exported"
 	banktypes "github.com/cosmos/cosmos-sdk/x/bank/types"
 
@@ -268,7 +268,7 @@ func (s *MempoolTestSuite) TestTxOrderWithOracle() {
 			orderedTxs := fetchTxs(itr, 1000)
 			numberTxOracle := 0
 			for _, tx := range orderedTxs {
-				if ante.IsOracleTx(tx.GetMsgs()) {
+				if helper.IsOracleTx(tx.GetMsgs()) {
 					numberTxOracle += +1
 				} else {
 					break
@@ -334,9 +334,9 @@ func (s *MempoolTestSuite) TestOracleTx() {
 	}
 	require.Equal(t, 3, len(orderedTxs))
 
-	require.True(t, ante.IsOracleTx(orderedTxs[0].GetMsgs()))
-	require.True(t, ante.IsOracleTx(orderedTxs[1].GetMsgs()))
-	require.False(t, ante.IsOracleTx(orderedTxs[2].GetMsgs()))
+	require.True(t, helper.IsOracleTx(orderedTxs[0].GetMsgs()))
+	require.True(t, helper.IsOracleTx(orderedTxs[1].GetMsgs()))
+	require.False(t, helper.IsOracleTx(orderedTxs[2].GetMsgs()))
 
 	require.Equal(t, 0, mp.CountTx())
 }
@@ -473,7 +473,7 @@ func (s *MempoolTestSuite) TestBatchTx_WhenEnoughMemPool() {
 	// Count oracle transactions in first batch
 	oracleCount := 0
 	for _, tx := range orderedTxs[:50] {
-		if ante.IsOracleTx(tx.GetMsgs()) {
+		if helper.IsOracleTx(tx.GetMsgs()) {
 			oracleCount++
 		}
 	}
@@ -575,7 +575,7 @@ func (s *MempoolTestSuite) TestBatchTx_WhenNotEnoughMemPool() {
 	firstRegularIndex := -1
 
 	for i, tx := range orderedTxs {
-		if ante.IsOracleTx(tx.GetMsgs()) {
+		if helper.IsOracleTx(tx.GetMsgs()) {
 			lastOracleIndex = i
 			// If we've already seen a regular transaction, this is an error
 			require.Equal(t, -1, firstRegularIndex,
diff --git a/custom/auth/ante/fee.go b/custom/auth/ante/fee.go
index 617fdf50..36fb7521 100644
--- a/custom/auth/ante/fee.go
+++ b/custom/auth/ante/fee.go
@@ -6,6 +6,7 @@ import (
 
 	errorsmod "cosmossdk.io/errors"
 
+	"github.com/classic-terra/core/v3/app/helper"
 	taxkeeper "github.com/classic-terra/core/v3/x/tax/keeper"
 	taxtypes "github.com/classic-terra/core/v3/x/tax/types"
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -234,7 +235,7 @@ func (fd FeeDecorator) checkTxFee(ctx sdk.Context, tx sdk.Tx, taxes sdk.Coins, n
 	feeCoins := feeTx.GetFee()
 	gas := feeTx.GetGas()
 	msgs := feeTx.GetMsgs()
-	isOracleTx := IsOracleTx(msgs)
+	isOracleTx := helper.IsOracleTx(msgs)
 	reverseCharge := false
 	refundNonTaxableTaxes := false
 
diff --git a/custom/auth/ante/fee_tax.go b/custom/auth/ante/fee_tax.go
index f8777512..37970cd7 100644
--- a/custom/auth/ante/fee_tax.go
+++ b/custom/auth/ante/fee_tax.go
@@ -10,7 +10,6 @@ import (
 	banktypes "github.com/cosmos/cosmos-sdk/x/bank/types"
 
 	marketexported "github.com/classic-terra/core/v3/x/market/exported"
-	oracleexported "github.com/classic-terra/core/v3/x/oracle/exported"
 )
 
 var IBCRegexp = regexp.MustCompile("^ibc/[a-fA-F0-9]{64}$")
@@ -121,21 +120,3 @@ func computeTax(ctx sdk.Context, tk TreasuryKeeper, th TaxKeeper, principal sdk.
 
 	return taxes
 }
-
-func IsOracleTx(msgs []sdk.Msg) bool {
-	if len(msgs) == 0 {
-		return false
-	}
-	for _, msg := range msgs {
-		switch msg.(type) {
-		case *oracleexported.MsgAggregateExchangeRatePrevote:
-			continue
-		case *oracleexported.MsgAggregateExchangeRateVote:
-			continue
-		default:
-			return false
-		}
-	}
-
-	return true
-}