diff --git a/docs/topics/i18n/internationalization.txt b/docs/topics/i18n/internationalization.txt
index cf009e4244..6b728d5f8e 100644
--- a/docs/topics/i18n/internationalization.txt
+++ b/docs/topics/i18n/internationalization.txt
@@ -500,6 +500,14 @@ apply.
 .. note:: The previous more verbose format is still supported:
    ``{% blocktrans with book|title as book_t and author|title as author_t %}``
 
+Reverse URL lookups cannot be carried out within the ``blocktrans`` and should
+be retrieved (and stored) beforehand::
+
+    {% url path.to.view arg arg2 as the_url %}
+    {% blocktrans %}
+    This is a URL: {{ the_url }}
+    {% endblocktrans %}
+
 .. _template-translation-vars:
 
 Other tags