diff --git a/js/background.js b/js/background.js
index 20ec8003f..f1a80de6f 100644
--- a/js/background.js
+++ b/js/background.js
@@ -700,7 +700,7 @@
         return;
       }
 
-      const nullAvatar = '';
+      const nullAvatar = undefined;
       if (avatar) {
         // would get to download this file on each client in the group
         // and reference the local file
@@ -831,7 +831,7 @@
           recipients: allMembers,
           active: true,
           expireTimer: 0,
-          avatar: '',
+          avatar: undefined,
         },
         confirm: () => {},
       };
diff --git a/ts/session/messages/outgoing/content/data/group/ClosedGroupUpdateMessage.ts b/ts/session/messages/outgoing/content/data/group/ClosedGroupUpdateMessage.ts
index 612f69eee..0664a0516 100644
--- a/ts/session/messages/outgoing/content/data/group/ClosedGroupUpdateMessage.ts
+++ b/ts/session/messages/outgoing/content/data/group/ClosedGroupUpdateMessage.ts
@@ -43,6 +43,13 @@ export abstract class ClosedGroupUpdateMessage extends ClosedGroupMessage {
       throw new Error('admins has not the correct type');
     }
 
+    if (
+      params.avatar !== undefined &&
+      !(params.avatar instanceof SignalService.AttachmentPointer)
+    ) {
+      throw new Error('avatar has not the correct type');
+    }
+
     this.name = params.name;
     this.members = params.members;
     this.admins = params.admins;