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 d3cd98a..6c5a072 100644
--- a/src/main/java/org/ntlab/acanthus_server/entities/InvitesJson.java
+++ b/src/main/java/org/ntlab/acanthus_server/entities/InvitesJson.java
@@ -8,7 +8,7 @@
 public class InvitesJson {
 
     @JsonProperty("invites")
-    private Collection<Integer> invites = new ArrayList<>();
+    private ArrayList<Integer> invites = new ArrayList<>();
 
     public  InvitesJson(Collection<Account> accounts) {
         for(Account inviter : accounts){