diff --git a/execution/gethexec/api.go b/execution/gethexec/api.go
index d3ff209e64..c58fbe7a1e 100644
--- a/execution/gethexec/api.go
+++ b/execution/gethexec/api.go
@@ -334,24 +334,26 @@ func (api *ArbTraceForwarderAPI) forward(ctx context.Context, method string, arg
 	return resp, nil
 }
 
-func (api *ArbTraceForwarderAPI) ClipToPostNitroGenesis(blockNumOrHash json.RawMessage) (json.RawMessage, error) {
+func (api *ArbTraceForwarderAPI) blockSupportedByClassicNode(blockNumOrHash json.RawMessage) error {
 	var bnh rpc.BlockNumberOrHash
 	err := bnh.UnmarshalJSON(blockNumOrHash)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	blockNum, isNum := bnh.Number()
 	if !isNum {
-		return blockNumOrHash, nil
+		return nil
 	}
 	blockNum, _ = api.blockchain.ClipToPostNitroGenesis(blockNum)
-	bnh.BlockNumber = &blockNum
-	return json.Marshal(bnh)
+	if blockNum < 0 || blockNum > rpc.BlockNumber(api.blockchain.Config().ArbitrumChainParams.GenesisBlockNum) {
+		return fmt.Errorf("block number %v is not supported by classic node", blockNum)
+	}
+	return nil
 }
 
 func (api *ArbTraceForwarderAPI) Call(ctx context.Context, callArgs json.RawMessage, traceTypes json.RawMessage, blockNumOrHash json.RawMessage) (*json.RawMessage, error) {
 	var err error
-	blockNumOrHash, err = api.ClipToPostNitroGenesis(blockNumOrHash)
+	err = api.blockSupportedByClassicNode(blockNumOrHash)
 	if err != nil {
 		return nil, err
 	}
@@ -360,7 +362,7 @@ func (api *ArbTraceForwarderAPI) Call(ctx context.Context, callArgs json.RawMess
 
 func (api *ArbTraceForwarderAPI) CallMany(ctx context.Context, calls json.RawMessage, blockNumOrHash json.RawMessage) (*json.RawMessage, error) {
 	var err error
-	blockNumOrHash, err = api.ClipToPostNitroGenesis(blockNumOrHash)
+	err = api.blockSupportedByClassicNode(blockNumOrHash)
 	if err != nil {
 		return nil, err
 	}
@@ -369,7 +371,7 @@ func (api *ArbTraceForwarderAPI) CallMany(ctx context.Context, calls json.RawMes
 
 func (api *ArbTraceForwarderAPI) ReplayBlockTransactions(ctx context.Context, blockNumOrHash json.RawMessage, traceTypes json.RawMessage) (*json.RawMessage, error) {
 	var err error
-	blockNumOrHash, err = api.ClipToPostNitroGenesis(blockNumOrHash)
+	err = api.blockSupportedByClassicNode(blockNumOrHash)
 	if err != nil {
 		return nil, err
 	}
@@ -390,7 +392,7 @@ func (api *ArbTraceForwarderAPI) Get(ctx context.Context, txHash json.RawMessage
 
 func (api *ArbTraceForwarderAPI) Block(ctx context.Context, blockNumOrHash json.RawMessage) (*json.RawMessage, error) {
 	var err error
-	blockNumOrHash, err = api.ClipToPostNitroGenesis(blockNumOrHash)
+	err = api.blockSupportedByClassicNode(blockNumOrHash)
 	if err != nil {
 		return nil, err
 	}