diff --git a/src/main/java/org/ntlab/acanthus_server/entities/InvitesJson.java b/src/main/java/org/ntlab/acanthus_server/entities/InvitesJson.java
index 6c5a072..8732c9b 100644
--- a/src/main/java/org/ntlab/acanthus_server/entities/InvitesJson.java
+++ b/src/main/java/org/ntlab/acanthus_server/entities/InvitesJson.java
@@ -16,7 +16,7 @@
         }
     }
 
-    public Collection<Integer> getInvitesJson() {
+    public ArrayList<Integer> getInvitesJson() {
         return invites;
     }