diff --git a/src/cmd/compile/internal/gc/export.go b/src/cmd/compile/internal/gc/export.go
index c1fea8aaad..b214d8fb97 100644
--- a/src/cmd/compile/internal/gc/export.go
+++ b/src/cmd/compile/internal/gc/export.go
@@ -173,13 +173,9 @@ func dumpexport() {
 
 		// verify that we can read the copied export data back in
 		// (use empty package map to avoid collisions)
-		savedPkgMap := types.PkgMap
-		savedPkgs := types.PkgList
-		types.PkgMap = make(map[string]*types.Pkg)
-		types.PkgList = nil
-		Import(types.NewPkg("", ""), bufio.NewReader(&copy)) // must not die
-		types.PkgList = savedPkgs
-		types.PkgMap = savedPkgMap
+		types.CleanroomDo(func() {
+			Import(types.NewPkg("", ""), bufio.NewReader(&copy)) // must not die
+		})
 	} else {
 		size = export(bout.Writer, Debug_export != 0)
 	}
diff --git a/src/cmd/compile/internal/gc/reflect.go b/src/cmd/compile/internal/gc/reflect.go
index 977c3d74c6..1703a9a67d 100644
--- a/src/cmd/compile/internal/gc/reflect.go
+++ b/src/cmd/compile/internal/gc/reflect.go
@@ -1501,10 +1501,8 @@ func dumptypestructs() {
 	}
 
 	// generate import strings for imported packages
-	for _, p := range types.PkgList {
-		if p.Direct {
-			dimportpath(p)
-		}
+	for _, p := range types.ImportedPkgList() {
+		dimportpath(p)
 	}
 
 	// do basic types if compiling package runtime.
diff --git a/src/cmd/compile/internal/types/pkg.go b/src/cmd/compile/internal/types/pkg.go
index b43f13e5d1..1fe49bd142 100644
--- a/src/cmd/compile/internal/types/pkg.go
+++ b/src/cmd/compile/internal/types/pkg.go
@@ -8,8 +8,12 @@ import (
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"fmt"
+	"sort"
 )
 
+// pkgMap maps a package path to a package.
+var pkgMap = make(map[string]*Pkg)
+
 type Pkg struct {
 	Path     string // string literal used in import statement, e.g. "runtime/internal/sys"
 	Name     string // package name, e.g. "sys"
@@ -20,14 +24,11 @@ type Pkg struct {
 	Syms     map[string]*Sym
 }
 
-var PkgMap = make(map[string]*Pkg)
-var PkgList []*Pkg
-
 // NewPkg returns a new Pkg for the given package path and name.
 // Unless name is the empty string, if the package exists already,
 // the existing package name and the provided name must match.
 func NewPkg(path, name string) *Pkg {
-	if p := PkgMap[path]; p != nil {
+	if p := pkgMap[path]; p != nil {
 		if name != "" && p.Name != name {
 			panic(fmt.Sprintf("conflicting package names %s and %s for path %q", p.Name, name, path))
 		}
@@ -39,12 +40,30 @@ func NewPkg(path, name string) *Pkg {
 	p.Name = name
 	p.Prefix = objabi.PathToPrefix(path)
 	p.Syms = make(map[string]*Sym)
-	PkgMap[path] = p
-	PkgList = append(PkgList, p)
+	pkgMap[path] = p
 
 	return p
 }
 
+// ImportedPkgList returns the list of directly imported packages.
+// The list is sorted by package path.
+func ImportedPkgList() []*Pkg {
+	var list []*Pkg
+	for _, p := range pkgMap {
+		if p.Direct {
+			list = append(list, p)
+		}
+	}
+	sort.Sort(byPath(list))
+	return list
+}
+
+type byPath []*Pkg
+
+func (a byPath) Len() int           { return len(a) }
+func (a byPath) Less(i, j int) bool { return a[i].Path < a[j].Path }
+func (a byPath) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+
 var nopkg = &Pkg{
 	Syms: make(map[string]*Sym),
 }
@@ -99,3 +118,12 @@ func InternString(b []byte) string {
 	}
 	return s
 }
+
+// CleanroomDo invokes f in an environment with with no preexisting packages.
+// For testing of import/export only.
+func CleanroomDo(f func()) {
+	saved := pkgMap
+	pkgMap = make(map[string]*Pkg)
+	f()
+	pkgMap = saved
+}