diff --git a/src/com/android/wallpaper/asset/BitmapUtils.java b/src/com/android/wallpaper/asset/BitmapUtils.java
index a627f0a..d1edaac 100755
--- a/src/com/android/wallpaper/asset/BitmapUtils.java
+++ b/src/com/android/wallpaper/asset/BitmapUtils.java
@@ -67,7 +67,9 @@
      */
     public static long generateHashCode(Bitmap bitmap) {
         long result = 17;
-
+        if (bitmap == null) {
+            return result;
+        }
         int width = bitmap.getWidth();
         int height = bitmap.getHeight();