diff --git a/packages/stream_chat_flutter/lib/src/user_mentions_overlay.dart b/packages/stream_chat_flutter/lib/src/user_mentions_overlay.dart
index d155ce4c..6068369a 100644
--- a/packages/stream_chat_flutter/lib/src/user_mentions_overlay.dart
+++ b/packages/stream_chat_flutter/lib/src/user_mentions_overlay.dart
@@ -30,7 +30,7 @@ class UserMentionsOverlay extends StatefulWidget {
           'Channel ${channel.cid} is not yet initialized',
         ),
         assert(
-          mentionAllAppUsers && client != null,
+          !mentionAllAppUsers || (mentionAllAppUsers && client != null),
           'StreamChatClient is required in order to use mentionAllAppUsers',
         ),
         super(key: key);