diff --git a/core/transaction/transactionchecker.go b/core/transaction/transactionchecker.go
index 3da17e8df..dcf642faf 100644
--- a/core/transaction/transactionchecker.go
+++ b/core/transaction/transactionchecker.go
@@ -38,7 +38,7 @@ func (t *DefaultChecker) SanityCheck(params interfaces.Parameters) elaerr.ELAErr
 
 	if err := t.parameters.Transaction.HeightVersionCheck(); err != nil {
 		log.Warn("[HeightVersionCheck],", err)
-		return elaerr.Simple(elaerr.ErrTxHeightVersion, nil)
+		return elaerr.Simple(elaerr.ErrTxHeightVersion, err)
 	}
 
 	if err := t.parameters.Transaction.CheckTransactionSize(); err != nil {
diff --git a/errors/errcode.go b/errors/errcode.go
index 7d800bfba..64115f809 100644
--- a/errors/errcode.go
+++ b/errors/errcode.go
@@ -95,7 +95,11 @@ type SimpleErr struct {
 
 func (e *SimpleErr) Error() string {
 	if len(e.message) == 0 {
-		return fmt.Sprintf("%s", ErrMap[e.code])
+		if e.inner != nil {
+			return fmt.Sprintf("%s:%s", ErrMap[e.code], e.inner.Error())
+		} else {
+			return fmt.Sprintf("%s", ErrMap[e.code])
+		}
 	} else {
 		return e.message
 	}
diff --git a/mempool/txpool.go b/mempool/txpool.go
index a8cec793d..4848a1456 100644
--- a/mempool/txpool.go
+++ b/mempool/txpool.go
@@ -95,20 +95,20 @@ func (mp *TxPool) appendToTxPool(tx interfaces.Transaction) elaerr.ELAError {
 		return elaerr.Simple(elaerr.ErrBlockIneffectiveCoinbase, nil)
 	}
 
-	if errCode := chain.CheckTransactionSanity(bestHeight+1, tx); errCode != nil {
+	if err := chain.CheckTransactionSanity(bestHeight+1, tx); err != nil {
 		log.Warn("[TxPool CheckTransactionSanity] failed", tx.Hash())
-		return errCode
+		return err
 	}
-	if _, errCode := chain.CheckTransactionContext(
-		bestHeight+1, tx, mp.proposalsUsedAmount, 0); errCode != nil {
+	if _, err := chain.CheckTransactionContext(
+		bestHeight+1, tx, mp.proposalsUsedAmount, 0); err != nil {
 		log.Warnf("[TxPool CheckTransactionContext] failed, hash: %s, err: %s", tx.Hash(),
-			errCode)
-		return errCode
+			err)
+		return err
 	}
 	//verify transaction by pool with lock
-	if errCode := mp.verifyTransactionWithTxnPool(tx); errCode != nil {
+	if err := mp.verifyTransactionWithTxnPool(tx); err != nil {
 		log.Warn("[TxPool verifyTransactionWithTxnPool] failed", tx.Hash())
-		return errCode
+		return err
 	}
 
 	size := tx.GetSize()
@@ -116,9 +116,9 @@ func (mp *TxPool) appendToTxPool(tx interfaces.Transaction) elaerr.ELAError {
 		log.Warn("TxPool check transactions size failed", tx.Hash())
 		return elaerr.Simple(elaerr.ErrTxPoolOverCapacity, nil)
 	}
-	if errCode := mp.AppendTx(tx); errCode != nil {
+	if err := mp.AppendTx(tx); err != nil {
 		log.Warn("[TxPool verifyTransactionWithTxnPool] failed", tx.Hash())
-		return errCode
+		return err
 	}
 	// Add the transaction to mem pool
 	if err := mp.doAddTransaction(tx); err != nil {