diff --git a/fusion_helpdesk/controllers/main.py b/fusion_helpdesk/controllers/main.py
index a515f546..3fb22ab5 100644
--- a/fusion_helpdesk/controllers/main.py
+++ b/fusion_helpdesk/controllers/main.py
@@ -598,9 +598,14 @@ class FusionHelpdeskController(http.Controller):
                 return {'ok': False, 'error': 'not_found',
                         'message': _('Ticket not found or not accessible.')}
             author_id = self._resolve_author(cfg, ident, found[0])
+            # We escape the user's text ourselves, then mark it up as paragraphs.
+            # message_post() ESCAPES a plain str body (it expects a Markup for
+            # HTML) — but Markup can't cross XML-RPC, so we pass body_is_html=True
+            # which tells the remote message_post to treat our already-escaped
+            # HTML as Markup. Without this the customer would see literal <p> tags.
             html = '<p>%s</p>' % _html_escape(text).replace('\n', '<br/>')
             self._rpc(cfg, 'helpdesk.ticket', 'message_post', [[ticket_id]], {
-                'body': html, 'message_type': 'comment',
+                'body': html, 'body_is_html': True, 'message_type': 'comment',
                 'subtype_xmlid': 'mail.mt_comment', 'author_id': author_id,
             })
             messages = self._public_messages(cfg, ticket_id)