diff --git a/synapse/handlers/e2e_room_keys.py b/synapse/handlers/e2e_room_keys.py
index f1b4424a0..854c181fc 100644
--- a/synapse/handlers/e2e_room_keys.py
+++ b/synapse/handlers/e2e_room_keys.py
@@ -207,6 +207,12 @@ class E2eRoomKeysHandler(object):
             changed = False  # if anything has changed, we need to update the etag
             for room_id, room in iteritems(room_keys["rooms"]):
                 for session_id, room_key in iteritems(room["sessions"]):
+                    if not isinstance(room_key["is_verified"], bool):
+                        msg = (
+                            "is_verified must be a boolean in keys for room %s" % room_id
+                        )
+                        raise SynapseError(400, msg, Codes.INVALID_PARAM)
+
                     log_kv(
                         {
                             "message": "Trying to upload room key",