diff --git a/go/packages/packagestest/modules.go b/go/packages/packagestest/modules.go
index 4608766ac0..42b62067a8 100644
--- a/go/packages/packagestest/modules.go
+++ b/go/packages/packagestest/modules.go
@@ -163,6 +163,7 @@ func (modules) Finalize(exported *Exported) error {
 	exported.Config.Env = append(exported.Config.Env,
 		"GO111MODULE=on",
 		"GOPATH="+filepath.Join(exported.temp, "modcache"),
+		"GOMODCACHE=",
 		"GOPROXY="+proxydir.ToURL(modProxyDir),
 		"GOSUMDB=off",
 	)
diff --git a/internal/imports/mod_test.go b/internal/imports/mod_test.go
index 5d73c88135..c6bbe56c20 100644
--- a/internal/imports/mod_test.go
+++ b/internal/imports/mod_test.go
@@ -688,6 +688,7 @@ func setup(t *testing.T, main, wd string) *modTest {
 	env := &ProcessEnv{
 		Env: map[string]string{
 			"GOPATH":      filepath.Join(dir, "gopath"),
+			"GOMODCACHE":  "",
 			"GO111MODULE": "on",
 			"GOSUMDB":     "off",
 			"GOPROXY":     proxydir.ToURL(proxyDir),