diff --git a/examples/echo_client.py b/examples/echo_client.py
index 9e07a43..e021920 100644
--- a/examples/echo_client.py
+++ b/examples/echo_client.py
@@ -156,6 +156,7 @@ class EchoBot(ClientXMPP):
                 # `encrypt_message` excepts the plaintext to be sent, a list of
                 # bare JIDs to encrypt to, and optionally a dict of problems to
                 # expect per bare JID.
+                # TODO: Document expect_problems
                 recipients = [mto]
                 encrypt = await self['xep_0384'].encrypt_message(body, recipients)
                 msg.append(encrypt)