diff --git a/protocol/lib/collections.go b/protocol/lib/collections.go
index e6f4fcebf4..a1377eb758 100644
--- a/protocol/lib/collections.go
+++ b/protocol/lib/collections.go
@@ -152,3 +152,13 @@ func MergeMaps[K comparable, V any](maps ...map[K]V) map[K]V {
 	}
 	return combinedMap
 }
+
+// Check if slice contains a particular value
+func SliceContains[T comparable](list []T, value T) bool {
+	for _, v := range list {
+		if v == value {
+			return true
+		}
+	}
+	return false
+}
diff --git a/protocol/lib/collections_test.go b/protocol/lib/collections_test.go
index 153489fc35..ced21c54c3 100644
--- a/protocol/lib/collections_test.go
+++ b/protocol/lib/collections_test.go
@@ -471,3 +471,15 @@ func TestMergeAllMapsWithDistinctKeys(t *testing.T) {
 		})
 	}
 }
+
+func TestSliceContains(t *testing.T) {
+	require.True(
+		t,
+		lib.SliceContains([]uint32{1, 2}, 1),
+	)
+
+	require.False(
+		t,
+		lib.SliceContains([]uint32{1, 2}, 3),
+	)
+}
diff --git a/protocol/x/accountplus/keeper/timestampnonce.go b/protocol/x/accountplus/keeper/timestampnonce.go
index 8dc5070c31..e23a0196a6 100644
--- a/protocol/x/accountplus/keeper/timestampnonce.go
+++ b/protocol/x/accountplus/keeper/timestampnonce.go
@@ -6,6 +6,7 @@ import (
 
 	"github.com/cosmos/cosmos-sdk/telemetry"
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/dydxprotocol/v4-chain/protocol/lib"
 	"github.com/dydxprotocol/v4-chain/protocol/lib/metrics"
 	"github.com/dydxprotocol/v4-chain/protocol/x/accountplus/types"
 )
@@ -80,6 +81,11 @@ func AttemptTimestampNonceUpdate(
 		return false
 	}
 
+	// Must be unique
+	if lib.SliceContains(tsNonceDetails.TimestampNonces, tsNonce) {
+		return false
+	}
+
 	if len(tsNonceDetails.TimestampNonces) < MaxTimestampNonceArrSize {
 		tsNonceDetails.TimestampNonces = append(tsNonceDetails.TimestampNonces, tsNonce)
 		return true
diff --git a/protocol/x/accountplus/keeper/timestampnonce_test.go b/protocol/x/accountplus/keeper/timestampnonce_test.go
index 9292f92ae9..9d283b88a1 100644
--- a/protocol/x/accountplus/keeper/timestampnonce_test.go
+++ b/protocol/x/accountplus/keeper/timestampnonce_test.go
@@ -127,7 +127,7 @@ func TestEjectStaleTsNonces(t *testing.T) {
 
 func TestAttemptTimestampNonceUpdate(t *testing.T) {
 	startTs := keeper.TimestampNonceSequenceCutoff
-	t.Run("Will not update if ts nonce <= maxEjectedNonce", func(t *testing.T) {
+	t.Run("Will reject ts nonce <= maxEjectedNonce", func(t *testing.T) {
 		tsNonce := startTs + 10
 
 		var tsNonces []uint64
@@ -157,7 +157,37 @@ func TestAttemptTimestampNonceUpdate(t *testing.T) {
 		require.Equal(t, expectedAccountState, accountState)
 	})
 
-	t.Run("Will update if ts nonces has capacity (ts nonce > maxEjectedNonce)", func(t *testing.T) {
+	t.Run("Will reject duplicate ts nonce", func(t *testing.T) {
+		tsNonce := startTs + 20
+
+		var tsNonces []uint64
+		for i := range 5 {
+			tsNonces = append(tsNonces, startTs+uint64(i)+20)
+		}
+
+		accountState := types.AccountState{
+			Address: constants.AliceAccAddress.String(),
+			TimestampNonceDetails: types.TimestampNonceDetails{
+				TimestampNonces: tsNonces,
+				MaxEjectedNonce: startTs + 10,
+			},
+		}
+
+		expectedAccountState := types.AccountState{
+			Address: constants.AliceAccAddress.String(),
+			TimestampNonceDetails: types.TimestampNonceDetails{
+				TimestampNonces: tsNonces,
+				MaxEjectedNonce: startTs + 10,
+			},
+		}
+
+		updated := keeper.AttemptTimestampNonceUpdate(tsNonce, &accountState)
+
+		require.False(t, updated)
+		require.Equal(t, expectedAccountState, accountState)
+	})
+
+	t.Run("Will update if ts nonces has capacity (given ts unique and ts > maxEjectedNonce)", func(t *testing.T) {
 		tsNonce := startTs + 11
 
 		var tsNonces []uint64
@@ -188,9 +218,9 @@ func TestAttemptTimestampNonceUpdate(t *testing.T) {
 	})
 
 	t.Run(
-		"Will not update if ts nonce <= existing ts nonces (timestamp nonce > maxEjectedNonce)",
+		"Will not update if ts nonce <= existing ts nonces (given ts unique and ts > maxEjectedNonce)",
 		func(t *testing.T) {
-			tsNonce := startTs + 20
+			tsNonce := startTs + 19
 
 			var tsNonces []uint64
 			for i := range keeper.MaxTimestampNonceArrSize {
@@ -220,15 +250,15 @@ func TestAttemptTimestampNonceUpdate(t *testing.T) {
 		})
 
 	t.Run(
-		"Will update if ts nonce larger than at least one existing ts nonce (timestamp nonce > maxEjectedNonce)",
+		"Will update if ts nonce larger than at least one existing ts nonce (given ts unique and ts > maxEjectedNonce)",
 		func(t *testing.T) {
-			tsNonce := startTs + 21
-
 			var tsNonces []uint64
 			for i := range keeper.MaxTimestampNonceArrSize {
 				tsNonces = append(tsNonces, startTs+uint64(i)+20)
 			}
 
+			tsNonce := tsNonces[len(tsNonces)-1] + 1
+
 			accountState := types.AccountState{
 				Address: constants.AliceAccAddress.String(),
 				TimestampNonceDetails: types.TimestampNonceDetails{