diff --git a/tests/AgentTests/FunctionalAPITests.hs b/tests/AgentTests/FunctionalAPITests.hs
index 522949ebe..bd62312f0 100644
--- a/tests/AgentTests/FunctionalAPITests.hs
+++ b/tests/AgentTests/FunctionalAPITests.hs
@@ -43,6 +43,7 @@ import Data.Int (Int64)
 import qualified Data.Map as M
 import Data.Maybe (isNothing)
 import qualified Data.Set as S
+import Data.Time.Clock (diffUTCTime, getCurrentTime)
 import Data.Time.Clock.System (SystemTime (..), getSystemTime)
 import Data.Type.Equality
 import SMPAgentClient
@@ -310,6 +311,7 @@ functionalAPITests t = do
   describe "Delivery receipts" $ do
     it "should send and receive delivery receipt" $ withSmpServer t testDeliveryReceipts
     it "should send delivery receipt only in connection v3+" $ testDeliveryReceiptsVersion t
+    it "send delivery receipts concurrently with messages" $ testDeliveryReceiptsConcurrent t
 
 testBasicAuth :: ATransport -> Bool -> (Maybe BasicAuth, Version) -> (Maybe BasicAuth, Version) -> (Maybe BasicAuth, Version) -> IO Int
 testBasicAuth t allowNewQueues srv@(srvAuth, srvVersion) clnt1 clnt2 = do
@@ -1928,6 +1930,57 @@ testDeliveryReceiptsVersion t = do
     disconnectAgentClient a'
     disconnectAgentClient b'
 
+testDeliveryReceiptsConcurrent :: (HasCallStack) => ATransport -> IO ()
+testDeliveryReceiptsConcurrent t =
+  withSmpServerConfigOn t cfg {msgQueueQuota = 128} testPort $ \_ -> do
+    withAgentClients2 $ \a b -> do
+      (aId, bId) <- runRight $ makeConnection a b
+      t1 <- liftIO getCurrentTime
+      concurrently_ (runClient "a" a bId) (runClient "b" b aId)
+      t2 <- liftIO getCurrentTime
+      diffUTCTime t2 t1 `shouldSatisfy` (< 15)
+      liftIO $ noMessages a "nothing else should be delivered to alice"
+      liftIO $ noMessages b "nothing else should be delivered to bob"
+  where
+    runClient :: String -> AgentClient -> ConnId -> IO ()
+    runClient _cName client connId = do
+      concurrently_ send receive
+      where
+        numMsgs = 100
+        send = runRight_ $
+          replicateM_ numMsgs $ do
+            -- liftIO $ print $ cName <> ": sendMessage"
+            void $ sendMessage client connId SMP.noMsgFlags "hello"
+        receive =
+          runRight_ $
+            -- for each sent message: 1 SENT, 1 RCVD, 1 OK for acknowledging RCVD
+            -- for each received message: 1 MSG, 1 OK for acknowledging MSG
+            receiveLoop (numMsgs * 5)
+        receiveLoop :: Int -> ExceptT AgentErrorType IO ()
+        receiveLoop 0 = pure ()
+        receiveLoop n = do
+          r <- getWithTimeout
+          case r of
+            (_, _, SENT _) -> do
+              -- liftIO $ print $ cName <> ": SENT"
+              pure ()
+            (_, _, MSG MsgMeta {recipient = (msgId, _), integrity = MsgOk} _ _) -> do
+              -- liftIO $ print $ cName <> ": MSG " <> show msgId
+              ackMessageAsync client (B.pack . show $ n) connId msgId (Just "")
+            (_, _, RCVD MsgMeta {recipient = (msgId, _), integrity = MsgOk} _) -> do
+              -- liftIO $ print $ cName <> ": RCVD " <> show msgId
+              ackMessageAsync client (B.pack . show $ n) connId msgId Nothing
+            (_, _, OK) -> do
+              -- liftIO $ print $ cName <> ": OK"
+              pure ()
+            r' -> error $ "unexpected event: " <> show r'
+          receiveLoop (n - 1)
+        getWithTimeout :: ExceptT AgentErrorType IO (AEntityTransmission 'AEConn)
+        getWithTimeout = do
+          1000000 `timeout` get client >>= \case
+            Just r -> pure r
+            _ -> error "timeout"
+
 testTwoUsers :: HasCallStack => IO ()
 testTwoUsers = withAgentClients2 $ \a b -> do
   let nc = netCfg initAgentServers