diff --git a/changelog.d/17336.bugfix b/changelog.d/17336.bugfix
new file mode 100644
index 0000000000..618834302e
--- /dev/null
+++ b/changelog.d/17336.bugfix
@@ -0,0 +1 @@
+Fix email notification subject when invited to a space.
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index 77cc69a71f..cf611bd90b 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -28,7 +28,7 @@ import jinja2
 from markupsafe import Markup
 from prometheus_client import Counter
 
-from synapse.api.constants import EventTypes, Membership, RoomTypes
+from synapse.api.constants import EventContentFields, EventTypes, Membership, RoomTypes
 from synapse.api.errors import StoreError
 from synapse.config.emailconfig import EmailSubjectConfig
 from synapse.events import EventBase
@@ -716,7 +716,8 @@ class Mailer:
                 )
                 if (
                     create_event
-                    and create_event.content.get("room_type") == RoomTypes.SPACE
+                    and create_event.content.get(EventContentFields.ROOM_TYPE)
+                    == RoomTypes.SPACE
                 ):
                     return self.email_subjects.invite_from_person_to_space % {
                         "person": inviter_name,