diff --git a/src/main/java/com/ntlab/irisserver/resources/GameStateRest.java b/src/main/java/com/ntlab/irisserver/resources/GameStateRest.java
index e44d178..ceb84a3 100644
--- a/src/main/java/com/ntlab/irisserver/resources/GameStateRest.java
+++ b/src/main/java/com/ntlab/irisserver/resources/GameStateRest.java
@@ -9,6 +9,7 @@
 
 import javax.ws.rs.*;
 import javax.ws.rs.core.MediaType;
+import java.util.ArrayList;
 import java.util.List;
 
 @Component
@@ -19,7 +20,7 @@
     @GET
     @Produces(MediaType.APPLICATION_JSON)
     public  List<Boolean> getOpens(@PathParam("rid") String rid){
-        List<Boolean> opens= null;
+        List<Boolean> opens= new ArrayList<>();
         RoomManager rm = RoomManager.getInstance();
         Room room = rm.getRoom(rid);
         Game game = room.getGame();