From 76c3be785c4d2592bbcfcc867c38afa7a334c2a2 Mon Sep 17 00:00:00 2001
From: Evgeny Poberezkin <evgeny@poberezkin.com>
Date: Sat, 28 Mar 2026 12:27:59 +0000
Subject: [PATCH] fix

---
 src/Simplex/Messaging/Server.hs                   | 4 ++--
 src/Simplex/Messaging/Server/MsgStore/Postgres.hs | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Simplex/Messaging/Server.hs b/src/Simplex/Messaging/Server.hs
index 78e038538..66100e97d 100644
--- a/src/Simplex/Messaging/Server.hs
+++ b/src/Simplex/Messaging/Server.hs
@@ -1377,8 +1377,8 @@ client
   where
     prefetchMsgs :: NonEmpty (VerifiedTransmission s) -> M s (Either ErrorType (Map RecipientId Message))
     prefetchMsgs batch =
-      let subQueues = [q | (Just (q, _), (_, _, Cmd SRecipient SUB)) <- L.toList batch]
-       in liftIO $ runExceptT $ tryPeekMsgs ms subQueues
+      let subQs = [q | (Just (q, _), (_, _, Cmd SRecipient SUB)) <- L.toList batch]
+       in if null subQs then pure $ Right M.empty else liftIO $ runExceptT $ tryPeekMsgs ms subQs
 
     processProxiedCmd :: Transmission (Command 'ProxiedClient) -> M s (Maybe ResponseAndMessage)
     processProxiedCmd (corrId, EntityId sessId, command) = (\t -> ((corrId, EntityId sessId, t), Nothing)) <$$> case command of
diff --git a/src/Simplex/Messaging/Server/MsgStore/Postgres.hs b/src/Simplex/Messaging/Server/MsgStore/Postgres.hs
index e51c8d483..b855346d4 100644
--- a/src/Simplex/Messaging/Server/MsgStore/Postgres.hs
+++ b/src/Simplex/Messaging/Server/MsgStore/Postgres.hs
@@ -246,7 +246,7 @@ instance MsgStoreClass PostgresMsgStore where
   tryPeekMsg ms q = isolateQueue ms q "tryPeekMsg" $ tryPeekMsg_ q ()
   {-# INLINE tryPeekMsg #-}
 
-  tryPeekMsgs :: PostgresMsgStore -> [PostgresQueue] -> ExceptT ErrorType IO (Map RecipientId Message)
+  tryPeekMsgs :: PostgresMsgStore -> [PostgresQueue] -> ExceptT ErrorType IO (M.Map RecipientId Message)
   tryPeekMsgs _ms [] = pure M.empty
   tryPeekMsgs ms qs =
     uninterruptibleMask_ $