diff --git a/changelogs/client_server/newsfragments/2216.clarification b/changelogs/client_server/newsfragments/2216.clarification
new file mode 100644
index 00000000..a777ad87
--- /dev/null
+++ b/changelogs/client_server/newsfragments/2216.clarification
@@ -0,0 +1 @@
+`room_id` is required for peeking via `/_matrix/client/v3/events`.
diff --git a/data/api/client-server/peeking_events.yaml b/data/api/client-server/peeking_events.yaml
index eaea5bbb..5867baa7 100644
--- a/data/api/client-server/peeking_events.yaml
+++ b/data/api/client-server/peeking_events.yaml
@@ -59,6 +59,7 @@ paths:
           example: "!somewhere:over.the.rainbow"
           schema:
             type: string
+          required: true
       responses:
         "200":
           description: The events received, which may be none.