diff --git a/src/go/types/api.go b/src/go/types/api.go
index ed62a785d6c..8c0d9d22bf2 100644
--- a/src/go/types/api.go
+++ b/src/go/types/api.go
@@ -101,12 +101,12 @@ type ImporterFrom interface {
 // A Config specifies the configuration for type checking.
 // The zero value for Config is a ready-to-use default configuration.
 type Config struct {
-	// GoVersion describes the accepted Go language version. The string
+	// goVersion describes the accepted Go language version. The string
 	// must follow the format "go%d.%d" (e.g. "go1.12") or it must be
 	// empty; an empty string indicates the latest language version.
 	// If the format is invalid, invoking the type checker will cause a
 	// panic.
-	GoVersion string
+	goVersion string
 
 	// If IgnoreFuncBodies is set, function bodies are not
 	// type-checked.
diff --git a/src/go/types/check.go b/src/go/types/check.go
index 25ea4906be3..a923c3c6121 100644
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -179,9 +179,9 @@ func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Ch
 		info = new(Info)
 	}
 
-	version, err := parseGoVersion(conf.GoVersion)
+	version, err := parseGoVersion(conf.goVersion)
 	if err != nil {
-		panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
+		panic(fmt.Sprintf("invalid Go version %q (%v)", conf.goVersion, err))
 	}
 
 	return &Checker{
diff --git a/src/go/types/check_test.go b/src/go/types/check_test.go
index c5dc93eade6..9c71277264b 100644
--- a/src/go/types/check_test.go
+++ b/src/go/types/check_test.go
@@ -240,7 +240,7 @@ func checkFiles(t *testing.T, sizes Sizes, goVersion string, filenames []string,
 	// typecheck and collect typechecker errors
 	var conf Config
 	conf.Sizes = sizes
-	conf.GoVersion = goVersion
+	SetGoVersion(&conf, goVersion)
 
 	// special case for importC.src
 	if len(filenames) == 1 {
diff --git a/src/go/types/stdlib_test.go b/src/go/types/stdlib_test.go
index 3dea8dcf1ed..503d0a6f445 100644
--- a/src/go/types/stdlib_test.go
+++ b/src/go/types/stdlib_test.go
@@ -134,7 +134,8 @@ func testTestDir(t *testing.T, path string, ignore ...string) {
 		// parse and type-check file
 		file, err := parser.ParseFile(fset, filename, nil, 0)
 		if err == nil {
-			conf := Config{GoVersion: goVersion, Importer: stdLibImporter}
+			conf := Config{Importer: stdLibImporter}
+			SetGoVersion(&conf, goVersion)
 			_, err = conf.Check(filename, fset, []*ast.File{file}, nil)
 		}
 
diff --git a/src/go/types/types_test.go b/src/go/types/types_test.go
index fd9462c4a27..25cd9966282 100644
--- a/src/go/types/types_test.go
+++ b/src/go/types/types_test.go
@@ -11,3 +11,9 @@ import "sync/atomic"
 // for tests where we may want to have a consistent
 // numbering for each individual test case.
 func ResetId() { atomic.StoreUint32(&lastId, 0) }
+
+// SetGoVersion sets the unexported goVersion field on config, so that tests
+// which assert on behavior for older Go versions can set it.
+func SetGoVersion(config *Config, goVersion string) {
+	config.goVersion = goVersion
+}