diff --git a/app/src/main/java/org/ntlab/radishforandroidstudio/framework/RWT/RWTButton.java b/app/src/main/java/org/ntlab/radishforandroidstudio/framework/RWT/RWTButton.java
index 38d66a6..ba01933 100644
--- a/app/src/main/java/org/ntlab/radishforandroidstudio/framework/RWT/RWTButton.java
+++ b/app/src/main/java/org/ntlab/radishforandroidstudio/framework/RWT/RWTButton.java
@@ -5,7 +5,7 @@
 import org.ntlab.radishforandroidstudio.framework.listener.TouchListener;
 
 public class RWTButton implements TouchListener {
-    private RWTSprite[] sprite = null;
+    private RWTSprite[] sprite = new RWTSprite[2];
 
     public RWTButton(final RWTLayer layer) {
         sprite = new RWTSprite[2];