diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index 24ac57f35d..853657d020 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -62,6 +62,8 @@ class VersionsRestServlet(RestServlet):
                     "org.matrix.msc2432": True,
                     # Implements additional endpoints as described in MSC2666
                     "uk.half-shot.msc2666": True,
+                    # Implements additional endpoints and features as described in MSC2403
+                    "xyz.amorgan.knock": True,
                 },
             },
         )