diff --git a/src/Simplex/Chat/Messages.hs b/src/Simplex/Chat/Messages.hs
index c846cc8563..fb876096a8 100644
--- a/src/Simplex/Chat/Messages.hs
+++ b/src/Simplex/Chat/Messages.hs
@@ -12,6 +12,7 @@
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE UndecidableInstances #-}
 {-# OPTIONS_GHC -fno-warn-ambiguous-fields #-}
 
 module Simplex.Chat.Messages where