diff --git a/integration/test/API/GalleyInternal.hs b/integration/test/API/GalleyInternal.hs
index e6354cf195..5df6c94d54 100644
--- a/integration/test/API/GalleyInternal.hs
+++ b/integration/test/API/GalleyInternal.hs
@@ -85,6 +85,21 @@ getFederationStatus user domains =
           $ req
           & addJSONObject ["domains" .= domainList]
 
+-- | Poll until the user's backend is fully connected to all given domains
+assertFullyConnected ::
+  ( HasCallStack,
+    MakesValue user
+  ) =>
+  user ->
+  [String] ->
+  App ()
+assertFullyConnected user domains =
+  eventually
+    $ bindResponse (getFederationStatus user domains)
+    $ \resp -> do
+      resp.status `shouldMatchInt` 200
+      resp.json %. "status" `shouldMatch` "fully-connected"
+
 -- | https://staging-nginz-https.zinfra.io/api-internal/swagger-ui/galley/#/galley/put_i_legalhold_whitelisted_teams__tid_
 legalholdWhitelistTeam :: (HasCallStack, MakesValue uid, MakesValue tid) => tid -> uid -> App Response
 legalholdWhitelistTeam tid uid = do
diff --git a/integration/test/Test/Conversation.hs b/integration/test/Test/Conversation.hs
index 3dd5615c66..681df7f59f 100644
--- a/integration/test/Test/Conversation.hs
+++ b/integration/test/Test/Conversation.hs
@@ -526,6 +526,10 @@ testAddUnreachableUserFromFederatingBackend domain = do
       otherDomain <- make domain & asString
       [alice, bob, charlie, chad] <-
         createAndConnectUsers [ownDomain, otherDomain, cDom.berDomain, cDom.berDomain]
+      -- Wait for ownDomain <-> {fed2, dynamicC} to be fully connected before
+      -- creating the conversation, so a transient fed2 reachability blip under
+      -- dynamic-backend churn does not turn the create into a 533 (WPB-3797).
+      assertFullyConnected alice [otherDomain, cDom.berDomain]
 
       conv <- withWebSockets [bob, charlie] $ \wss -> do
         conv <-