diff --git a/core/state_transition.go b/core/state_transition.go
index b74a2766d19e..8dc521b9c141 100644
--- a/core/state_transition.go
+++ b/core/state_transition.go
@@ -202,7 +202,7 @@ func (st *StateTransition) buyGas() error {
 			return fmt.Errorf("%w: fee delegation type not supported", ErrTxTypeNotSupported)
 		}
 		FDmgval := new(big.Int).SetUint64(st.msg.Gas())
-		FDmgval = FDmgval.Mul(FDmgval, st.gasFeeCap)
+		FDmgval = FDmgval.Mul(FDmgval, st.gasPrice)
 		feePayer := *st.msg.FeePayer()
 		if feePayer == st.msg.From() {
 			FDbalanceCheck := new(big.Int).SetUint64(st.msg.Gas())
diff --git a/core/tx_pool.go b/core/tx_pool.go
index e4b1ed565e6f..ee1db92cb154 100644
--- a/core/tx_pool.go
+++ b/core/tx_pool.go
@@ -707,8 +707,11 @@ func (pool *TxPool) validateTx(tx *types.Transaction, local bool) error {
 	// fee delegation
 	if tx.Type() == types.FeeDelegateDynamicFeeTxType {
 		// Make sure the transaction is signed properly.
+		if tx.FeePayer() == nil {
+			return ErrInvalidFeePayer
+		}
 		feePayer, err := types.FeePayer(types.NewFeeDelegateSigner(pool.chainconfig.ChainID), tx)
-		if *tx.FeePayer() != feePayer || err != nil {
+		if err != nil || *tx.FeePayer() != feePayer {
 			return ErrInvalidFeePayer
 		}
 		if pool.currentState.GetBalance(feePayer).Cmp(tx.FeePayerCost()) < 0 {
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index 74e058d6ca38..f5404ef90f4e 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -1714,6 +1714,10 @@ func SubmitTransaction(ctx context.Context, b Backend, tx *types.Transaction) (c
 		// Ensure only eip155 signed transactions are submitted if EIP155Required is set.
 		return common.Hash{}, errors.New("only replay-protected (EIP-155) transactions allowed over RPC")
 	}
+	// fee delegation
+	if tx.Type() == types.FeeDelegateDynamicFeeTxType && tx.FeePayer() == nil {
+		return common.Hash{}, errors.New("FeePayer address is null")
+	}
 	if err := b.SendTx(ctx, tx); err != nil {
 		return common.Hash{}, err
 	}