diff --git a/changelog.d/16842.misc b/changelog.d/16842.misc
new file mode 100644
index 000000000..022ace7d9
--- /dev/null
+++ b/changelog.d/16842.misc
@@ -0,0 +1 @@
+Add support for stabilised [MSC3981](https://github.com/matrix-org/matrix-spec-proposals/pull/3981) that adds a `recurse` parameter on the `/relations` API.
diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py
index e8dfeaa54..42da017f3 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -71,7 +71,7 @@ class RelationPaginationServlet(RestServlet):
             self._store, request, default_limit=5, default_dir=Direction.BACKWARDS
         )
         if self._support_recurse:
-            recurse = parse_boolean(
+            recurse = parse_boolean(request, "recurse", default=False) or parse_boolean(
                 request, "org.matrix.msc3981.recurse", default=False
             )
         else: