diff --git a/changelog.d/6020.bugfix b/changelog.d/6020.bugfix
new file mode 100644
index 000000000..58a7deba9
--- /dev/null
+++ b/changelog.d/6020.bugfix
@@ -0,0 +1 @@
+Ensure support users can be registered even if MAU limit is reached.
diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index ddc195bc3..9e445cd80 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -25,7 +25,7 @@ from twisted.internet import defer
 import synapse.logging.opentracing as opentracing
 import synapse.types
 from synapse import event_auth
-from synapse.api.constants import EventTypes, JoinRules, Membership
+from synapse.api.constants import EventTypes, JoinRules, Membership, UserTypes
 from synapse.api.errors import (
     AuthError,
     Codes,
@@ -709,7 +709,7 @@ class Auth(object):
             )
 
     @defer.inlineCallbacks
-    def check_auth_blocking(self, user_id=None, threepid=None):
+    def check_auth_blocking(self, user_id=None, threepid=None, user_type=None):
         """Checks if the user should be rejected for some external reason,
         such as monthly active user limiting or global disable flag
 
@@ -722,6 +722,9 @@ class Auth(object):
                 with a MAU blocked server, normally they would be rejected but their
                 threepid is on the reserved list. user_id and
                 threepid should never be set at the same time.
+
+            user_type(str|None): If present, is used to decide whether to check against
+                certain blocking reasons like MAU.
         """
 
         # Never fail an auth check for the server notices users or support user
@@ -759,6 +762,10 @@ class Auth(object):
                     self.hs.config.mau_limits_reserved_threepids, threepid
                 ):
                     return
+            elif user_type == UserTypes.SUPPORT:
+                # If the user does not exist yet and is of type "support",
+                # allow registration. Support users are excluded from MAU checks.
+                return
             # Else if there is no room in the MAU bucket, bail
             current_mau = yield self.store.get_monthly_active_count()
             if current_mau >= self.hs.config.max_mau_value:
diff --git a/tests/api/test_auth.py b/tests/api/test_auth.py
index c0cb8ef29..6121efcfa 100644
--- a/tests/api/test_auth.py
+++ b/tests/api/test_auth.py
@@ -21,6 +21,7 @@ from twisted.internet import defer
 
 import synapse.handlers.auth
 from synapse.api.auth import Auth
+from synapse.api.constants import UserTypes
 from synapse.api.errors import (
     AuthError,
     Codes,
@@ -335,6 +336,23 @@ class AuthTestCase(unittest.TestCase):
         )
         yield self.auth.check_auth_blocking()
 
+    @defer.inlineCallbacks
+    def test_blocking_mau__depending_on_user_type(self):
+        self.hs.config.max_mau_value = 50
+        self.hs.config.limit_usage_by_mau = True
+
+        self.store.get_monthly_active_count = Mock(return_value=defer.succeed(100))
+        # Support users allowed
+        yield self.auth.check_auth_blocking(user_type=UserTypes.SUPPORT)
+        self.store.get_monthly_active_count = Mock(return_value=defer.succeed(100))
+        # Bots not allowed
+        with self.assertRaises(ResourceLimitError):
+            yield self.auth.check_auth_blocking(user_type=UserTypes.BOT)
+        self.store.get_monthly_active_count = Mock(return_value=defer.succeed(100))
+        # Real users not allowed
+        with self.assertRaises(ResourceLimitError):
+            yield self.auth.check_auth_blocking()
+
     @defer.inlineCallbacks
     def test_reserved_threepid(self):
         self.hs.config.limit_usage_by_mau = True