diff --git a/go/types/labels.go b/go/types/labels.go
index fe0319c8..d6ffc523 100644
--- a/go/types/labels.go
+++ b/go/types/labels.go
@@ -131,7 +131,7 @@ func (check *Checker) blockBranches(all *Scope, parent *block, lstmt *ast.Labele
 		case *ast.LabeledStmt:
 			// declare non-blank label
 			if name := s.Label.Name; name != "_" {
-				lbl := NewLabel(s.Label.Pos(), name)
+				lbl := NewLabel(s.Label.Pos(), check.pkg, name)
 				if alt := all.Insert(lbl); alt != nil {
 					check.softErrorf(lbl.pos, "label %s already declared", name)
 					check.reportAltDecl(alt)
diff --git a/go/types/object.go b/go/types/object.go
index 4c2a8ca0..a495f85c 100644
--- a/go/types/object.go
+++ b/go/types/object.go
@@ -201,8 +201,8 @@ type Label struct {
 	object
 }
 
-func NewLabel(pos token.Pos, name string) *Label {
-	return &Label{object{pos: pos, name: name, typ: Typ[Invalid]}}
+func NewLabel(pos token.Pos, pkg *Package, name string) *Label {
+	return &Label{object{pos: pos, pkg: pkg, name: name, typ: Typ[Invalid]}}
 }
 
 // A Builtin represents a built-in function.
diff --git a/go/types/stdlib_test.go b/go/types/stdlib_test.go
index 44aef2f4..8a6a9bb2 100644
--- a/go/types/stdlib_test.go
+++ b/go/types/stdlib_test.go
@@ -174,8 +174,25 @@ func typecheck(t *testing.T, path string, filenames []string) {
 	// typecheck package files
 	var conf Config
 	conf.Error = func(err error) { t.Error(err) }
-	conf.Check(path, fset, files, nil)
+	info := Info{Uses: make(map[*ast.Ident]Object)}
+	conf.Check(path, fset, files, &info)
 	pkgCount++
+
+	// Perform checks of API invariants.
+
+	// All Objects have a package, except predeclared ones.
+	errorError := Universe.Lookup("error").Type().Underlying().(*Interface).ExplicitMethod(0) // (error).Error
+	for id, obj := range info.Uses {
+		predeclared := obj == Universe.Lookup(obj.Name()) || obj == errorError
+		if predeclared == (obj.Pkg() != nil) {
+			posn := fset.Position(id.Pos())
+			if predeclared {
+				t.Errorf("%s: predeclared object with package: %s", posn, obj)
+			} else {
+				t.Errorf("%s: user-defined object without package: %s", posn, obj)
+			}
+		}
+	}
 }
 
 // pkgFilenames returns the list of package filenames for the given directory.