diff --git a/ast.go b/ast.go
index b0bd140b..4c95a49c 100644
--- a/ast.go
+++ b/ast.go
@@ -83,6 +83,8 @@ func toType(typ types.Type) ast.Expr {
 	switch t := typ.(type) {
 	case *types.Basic: // bool, int, etc
 		return toBasicType(t)
+	case *types.Interface:
+		return toInterface(t)
 	case *types.Slice:
 		return toSliceType(t)
 	case *types.Array:
@@ -108,6 +110,21 @@ func toArrayType(t *types.Array) ast.Expr {
 	return &ast.ArrayType{Len: len, Elt: toType(t.Elem())}
 }
 
+func toInterface(t *types.Interface) ast.Expr {
+	var flds []*ast.Field
+	for i, n := 0, t.NumExplicitMethods(); i < n; i++ {
+		fn := t.ExplicitMethod(i)
+		name := ident(fn.Name())
+		typ := toFuncType(fn.Type().(*types.Signature))
+		fld := &ast.Field{Names: []*ast.Ident{name}, Type: typ}
+		flds = append(flds, fld)
+	}
+	for i, n := 0, t.NumEmbeddeds(); i < n; i++ {
+		panic("TODO: interface embedded")
+	}
+	return &ast.InterfaceType{Methods: &ast.FieldList{List: flds}}
+}
+
 // -----------------------------------------------------------------------------
 // expression
 
diff --git a/package_test.go b/package_test.go
index 094549cb..4f8f193e 100644
--- a/package_test.go
+++ b/package_test.go
@@ -20,7 +20,7 @@ func domTest(t *testing.T, pkg *gox.Package, expected string) {
 	}
 	result := b.String()
 	if result != expected {
-		t.Fatalf("\nResult:\n%s\nExpected:%s\n", result, expected)
+		t.Fatalf("\nResult:\n%s\nExpected:\n%s\n", result, expected)
 	}
 }
 
@@ -62,6 +62,39 @@ func main() {
 `)
 }
 
+func TestEmptyInterface(t *testing.T) {
+	pkg := gox.NewPackage("", "main", nil)
+	v := pkg.NewParam("v", types.NewSlice(types.NewInterfaceType(nil, nil)))
+	pkg.NewFunc(nil, "foo", gox.NewTuple(v), nil, true).BodyStart(pkg).End()
+	pkg.NewFunc(nil, "main", nil, nil, false).BodyStart(pkg).End()
+	domTest(t, pkg, `package main
+
+func foo(v ...interface {
+}) {
+}
+func main() {
+}
+`)
+}
+
+func TestInterfaceMethods(t *testing.T) {
+	pkg := gox.NewPackage("", "main", nil)
+	bar := types.NewFunc(token.NoPos, pkg.Types, "Bar", types.NewSignature(nil, nil, nil, false))
+	methods := []*types.Func{bar}
+	v := pkg.NewParam("v", types.NewSlice(types.NewInterfaceType(methods, nil)))
+	pkg.NewFunc(nil, "foo", gox.NewTuple(v), nil, true).BodyStart(pkg).End()
+	pkg.NewFunc(nil, "main", nil, nil, false).BodyStart(pkg).End()
+	domTest(t, pkg, `package main
+
+func foo(v ...interface {
+	Bar()
+}) {
+}
+func main() {
+}
+`)
+}
+
 func TestGoTypesPkg(t *testing.T) {
 	const src = `package foo