diff --git a/rpc/client.go b/rpc/client.go
index edd9ecf1b..e43760c22 100644
--- a/rpc/client.go
+++ b/rpc/client.go
@@ -17,7 +17,6 @@
 package rpc
 
 import (
-	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -360,7 +359,10 @@ func (c *Client) BatchCall(b []BatchElem) error {
 //
 // Note that batch calls may not be executed atomically on the server side.
 func (c *Client) BatchCallContext(ctx context.Context, b []BatchElem) error {
-	msgs := make([]*jsonrpcMessage, len(b))
+	var (
+		msgs = make([]*jsonrpcMessage, len(b))
+		byID = make(map[string]int, len(b))
+	)
 	op := &requestOp{
 		ids:  make([]json.RawMessage, len(b)),
 		resp: make(chan *jsonrpcMessage, len(b)),
@@ -372,6 +374,7 @@ func (c *Client) BatchCallContext(ctx context.Context, b []BatchElem) error {
 		}
 		msgs[i] = msg
 		op.ids[i] = msg.ID
+		byID[string(msg.ID)] = i
 	}
 
 	var err error
@@ -391,13 +394,7 @@ func (c *Client) BatchCallContext(ctx context.Context, b []BatchElem) error {
 		// Find the element corresponding to this response.
 		// The element is guaranteed to be present because dispatch
 		// only sends valid IDs to our channel.
-		var elem *BatchElem
-		for i := range msgs {
-			if bytes.Equal(msgs[i].ID, resp.ID) {
-				elem = &b[i]
-				break
-			}
-		}
+		elem := &b[byID[string(resp.ID)]]
 		if resp.Error != nil {
 			elem.Error = resp.Error
 			continue