diff --git a/keys.go b/keys.go
index c77eeb248..b8aa7e7ac 100644
--- a/keys.go
+++ b/keys.go
@@ -30,14 +30,3 @@ const (
 	KeySpace = Key(ui.KeySpace)
 	KeyMax   = Key(ui.KeyMax)
 )
-
-// A MouseButton represents a mouse button.
-type MouseButton int
-
-// MouseButtons
-const (
-	MouseButtonLeft   = MouseButton(ui.MouseButtonLeft)
-	MouseButtonRight  = MouseButton(ui.MouseButtonRight)
-	MouseButtonMiddle = MouseButton(ui.MouseButtonMiddle)
-	MouseButtonMax    = MouseButton(ui.MouseButtonMax)
-)
diff --git a/mousebuttons.go b/mousebuttons.go
new file mode 100644
index 000000000..9f59cc2b9
--- /dev/null
+++ b/mousebuttons.go
@@ -0,0 +1,30 @@
+// Copyright 2015 Hajime Hoshi
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ebiten
+
+import (
+	"github.com/hajimehoshi/ebiten/internal/ui"
+)
+
+// A MouseButton represents a mouse button.
+type MouseButton int
+
+// MouseButtons
+const (
+	MouseButtonLeft   = MouseButton(ui.MouseButtonLeft)
+	MouseButtonRight  = MouseButton(ui.MouseButtonRight)
+	MouseButtonMiddle = MouseButton(ui.MouseButtonMiddle)
+	MouseButtonMax    = MouseButton(ui.MouseButtonMax)
+)