diff --git a/config/config.go b/config/config.go
index bb289037a..14c4d419f 100644
--- a/config/config.go
+++ b/config/config.go
@@ -840,7 +840,7 @@ func DefaultMempoolConfig() *MempoolConfig {
 		MaxPendingTxsBytes:           1024 * 1024 * 1024, // 1GB
 		PendingTTLDuration:           0 * time.Second,
 		PendingTTLNumBlocks:          0,
-		RemoveExpiredTxsFromQueue:    false,
+		RemoveExpiredTxsFromQueue:    true,
 	}
 }
 
diff --git a/internal/mempool/mempool.go b/internal/mempool/mempool.go
index 25e3aa524..25302cc9c 100644
--- a/internal/mempool/mempool.go
+++ b/internal/mempool/mempool.go
@@ -308,6 +308,16 @@ func (txmp *TxMempool) CheckTx(
 		return types.ErrTxInCache
 	}
 
+	// Check if mempool is full before executing CheckTx
+	numTxs := txmp.NumTxsNotPending()
+	if numTxs >= txmp.config.Size-1 && txmp.config.Size > 5000 {
+		return types.ErrMempoolIsFull{
+			NumTxs:      numTxs,
+			MaxTxs:      txmp.config.Size,
+			MaxTxsBytes: txmp.config.MaxTxsBytes,
+		}
+	}
+
 	res, err := txmp.proxyAppConn.CheckTx(ctx, &abci.RequestCheckTx{Tx: tx})
 
 	// when a transaction is removed/expired/rejected, this should be called