diff --git a/changelog.d/3879.bugfix b/changelog.d/3879.bugfix
new file mode 100644
index 0000000000000000000000000000000000000000..82cb2a8ebc49d90ad48cd7543cff21616f600de7
--- /dev/null
+++ b/changelog.d/3879.bugfix
@@ -0,0 +1 @@
+Don't ratelimit autojoins
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 1e53f2c635c3c17e8943fa6afb57111b33c23dae..da914c46ffe4f49897fe8471804336c4442898e9 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -534,4 +534,5 @@ class RegistrationHandler(BaseHandler):
             room_id=room_id,
             remote_room_hosts=remote_room_hosts,
             action="join",
+            ratelimit=False,
         )