diff --git a/addons/mail/static/src/core/channel_member_service.js b/addons/mail/static/src/core/channel_member_service.js
index b6d1637b4cd..2cfbfb7aa35 100644
--- a/addons/mail/static/src/core/channel_member_service.js
+++ b/addons/mail/static/src/core/channel_member_service.js
@@ -37,7 +37,7 @@ export class ChannelMemberService {
         switch (command) {
             case "insert":
                 {
-                    if (!member.thread.channelMembers.includes(member)) {
+                    if (!member.thread?.channelMembers?.includes(member)) {
                         member.thread.channelMembers.push(member);
                     }
                 }