diff --git a/changelog.d/5974.feature b/changelog.d/5974.feature
new file mode 100644
index 000000000..387a444fc
--- /dev/null
+++ b/changelog.d/5974.feature
@@ -0,0 +1 @@
+Add m.id_access_token to unstable_features in /versions as per MSC2264.
\ No newline at end of file
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index 3c9ec59d7..fdab0ddb4 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -50,6 +50,9 @@ class VersionsRestServlet(RestServlet):
                 # as per MSC1497:
                 "unstable_features": {
                     "m.lazy_load_members": True,
+                    # as per MSC2190, as amended by MSC2264
+                    # to be removed in r0.6.0
+                    "m.id_access_token": True,
                     # Advertise to clients that they need not include an `id_server`
                     # parameter during registration or password reset, as Synapse now decides
                     # itself which identity server to use (or none at all).