diff --git a/go/tools/gopackagesdriver/json_packages_driver.go b/go/tools/gopackagesdriver/json_packages_driver.go
index 9bbf34081a..d91f2ed114 100644
--- a/go/tools/gopackagesdriver/json_packages_driver.go
+++ b/go/tools/gopackagesdriver/json_packages_driver.go
@@ -16,7 +16,7 @@ package main
 
 import (
 	"fmt"
-	"go/types"
+	"runtime"
 )
 
 type JSONPackagesDriver struct {
@@ -52,7 +52,8 @@ func (b *JSONPackagesDriver) GetResponse(labels []string) *driverResponse {
 
 	return &driverResponse{
 		NotHandled: false,
-		Sizes:      types.SizesFor("gc", "amd64").(*types.StdSizes),
+		Compiler:   "gc",
+		Arch:       runtime.GOARCH,
 		Roots:      rootPkgs,
 		Packages:   packages,
 	}
diff --git a/go/tools/gopackagesdriver/main.go b/go/tools/gopackagesdriver/main.go
index fea2d2c141..8cc904d3ce 100644
--- a/go/tools/gopackagesdriver/main.go
+++ b/go/tools/gopackagesdriver/main.go
@@ -18,8 +18,8 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"go/types"
 	"os"
+	"runtime"
 	"strings"
 )
 
@@ -31,8 +31,10 @@ type driverResponse struct {
 	// lists of multiple drivers, go/packages will fall back to the next driver.
 	NotHandled bool
 
-	// Sizes, if not nil, is the types.Sizes to use when type checking.
-	Sizes *types.StdSizes
+	// Compiler and Arch are the arguments pass of types.SizesFor
+	// to get a types.Sizes to use when type checking.
+	Compiler string
+	Arch     string
 
 	// Roots is the set of package IDs that make up the root packages.
 	// We have to encode this separately because when we encode a single package
@@ -63,7 +65,8 @@ var (
 	additionalKinds       = strings.Fields(os.Getenv("GOPACKAGESDRIVER_BAZEL_KINDS"))
 	emptyResponse         = &driverResponse{
 		NotHandled: true,
-		Sizes:      types.SizesFor("gc", "amd64").(*types.StdSizes),
+		Compiler:   "gc",
+		Arch:       runtime.GOARCH,
 		Roots:      []string{},
 		Packages:   []*FlatPackage{},
 	}