diff --git a/eth/tracers/api.go b/eth/tracers/api.go
index 978854751c..7613a59cb4 100644
--- a/eth/tracers/api.go
+++ b/eth/tracers/api.go
@@ -440,7 +440,7 @@ func (api *API) TraceBlockByHash(ctx context.Context, hash common.Hash, config *
 
 // TraceBlock returns the structured logs created during the execution of EVM
 // and returns them as a JSON object.
-func (api *API) TraceBlock(ctx context.Context, blob []byte, config *TraceConfig) ([]*txTraceResult, error) {
+func (api *API) TraceBlock(ctx context.Context, blob hexutil.Bytes, config *TraceConfig) ([]*txTraceResult, error) {
 	block := new(types.Block)
 	if err := rlp.Decode(bytes.NewReader(blob), block); err != nil {
 		return nil, fmt.Errorf("could not decode block: %v", err)