diff --git a/synapse/federation/sender/per_destination_queue.py b/synapse/federation/sender/per_destination_queue.py
index 2d896448d7..97109399d2 100644
--- a/synapse/federation/sender/per_destination_queue.py
+++ b/synapse/federation/sender/per_destination_queue.py
@@ -194,9 +194,6 @@ class PerDestinationQueue(object):
                 # We have to keep 2 free slots for presence and rr_edus
                 limit = MAX_EDUS_PER_TRANSACTION - 2
 
-                # Lock before we start doing work
-                acquired_lock = yield make_deferred_yieldable(self._transaction_manager.limiter.acquire())
-
                 device_update_edus, dev_list_id = (
                     yield self._get_device_update_edus(limit)
                 )
@@ -207,6 +204,9 @@ class PerDestinationQueue(object):
                     yield self._get_to_device_message_edus(limit)
                 )
 
+                # Lock before we start doing work
+                acquired_lock = yield make_deferred_yieldable(self._transaction_manager.limiter.acquire())
+
                 pending_edus = device_update_edus + to_device_edus
 
                 # BEGIN CRITICAL SECTION