diff --git a/sgx-bwmsgsv2.rb b/sgx-bwmsgsv2.rb
index afdd9fc7638bddc309aaa00fbc0821f9c835b41c..0eebd4d2adbd1f6885b110b23f23f1d9de4104b4 100755
--- a/sgx-bwmsgsv2.rb
+++ b/sgx-bwmsgsv2.rb
@@ -1133,7 +1133,10 @@ class WebhookHandler < Goliath::API
 			unless msg || text.to_s.empty?
 				msg = Blather::Stanza::Message.new(
 					bare_jid,
-					# TODO: The numbers, what do they mean?
+					# Strip control codes.
+					# This only happened, or at least caused a problem, once,
+					# but it seems sensible to say that we shouldn't be getting
+					# control codes from the PSTN.
 					text.gsub(/[\u0000-\u0008\u000b-\u001f]/, "")
 				)
 				msg.document.encoding = "utf-8"