diff --git a/changelog.d/13235.bugfix b/changelog.d/13235.bugfix
new file mode 100644
index 000000000000..5c31fbc7755d
--- /dev/null
+++ b/changelog.d/13235.bugfix
@@ -0,0 +1 @@
+Fix MSC3202-enabled appservices not receiving to-device messages, preventing messages from being decrypted.
\ No newline at end of file
diff --git a/synapse/appservice/scheduler.py b/synapse/appservice/scheduler.py
index de5e5216c223..edaf3b2c2ca6 100644
--- a/synapse/appservice/scheduler.py
+++ b/synapse/appservice/scheduler.py
@@ -329,8 +329,9 @@ async def _compute_msc3202_otk_counts_and_fallback_keys(
             )
 
         # Add recipients of to-device messages.
-        # device_message["user_id"] is the ID of the recipient.
-        users.update(device_message["user_id"] for device_message in to_device_messages)
+        users.update(
+            device_message["to_user_id"] for device_message in to_device_messages
+        )
 
         # Compute and return the counts / fallback key usage states
         otk_counts = await self._store.count_bulk_e2e_one_time_keys_for_as(users)