diff --git a/changelog.d/15558.misc b/changelog.d/15558.misc
new file mode 100644
index 0000000000..a7cfee2513
--- /dev/null
+++ b/changelog.d/15558.misc
@@ -0,0 +1 @@
+Add `org.matrix.msc3981` info to `client/versions`.
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index e9b56fc3f8..58c5b07390 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -126,6 +126,8 @@ class VersionsRestServlet(RestServlet):
                     "org.matrix.msc3912": self.config.experimental.msc3912_enabled,
                     # Adds support for unstable "intentional mentions" behaviour.
                     "org.matrix.msc3952_intentional_mentions": self.config.experimental.msc3952_intentional_mentions,
+                    # Whether recursively provide relations is supported.
+                    "org.matrix.msc3981": self.config.experimental.msc3981_recurse_relations,
                     # Adds support for deleting account data.
                     "org.matrix.msc3391": self.config.experimental.msc3391_enabled,
                 },