diff --git a/app/src/main/rs/blur_generated.rsh b/app/src/main/rs/blur_generated.rsh
index 31cb9a3..178e53b 100644
--- a/app/src/main/rs/blur_generated.rsh
+++ b/app/src/main/rs/blur_generated.rsh
@@ -1399,6 +1399,8 @@ static uchar value_blur(int pixel, int begin, int end)
 			3 * value_buffer[i+64] +
 			3 * value_buffer[i+65]) >> 14;
 	default:
+		if (i < begin || end <= i)
+			return 0;
 		return value_buffer[i];
 	}
 	return 0;
diff --git a/utils/blur.c b/utils/blur.c
index 3b57a44..24183c2 100644
--- a/utils/blur.c
+++ b/utils/blur.c
@@ -67,6 +67,6 @@ int main()
 		printf("\tcase %d:\n", i);
 		emit((1 << i) | 1);
 	}
-	printf("\tdefault:\n\t\treturn value_buffer[i];\n\t}\n\treturn 0;\n}\n");
+	printf("\tdefault:\n\t\tif (i < begin || end <= i)\n\t\t\treturn 0;\n\t\treturn value_buffer[i];\n\t}\n\treturn 0;\n}\n");
 	return 0;
 }