diff --git a/docs/topics/testing/tools.txt b/docs/topics/testing/tools.txt
index 90da7d91c7..b2ad760f00 100644
--- a/docs/topics/testing/tools.txt
+++ b/docs/topics/testing/tools.txt
@@ -1753,7 +1753,8 @@ your test suite.
 
 .. method:: SimpleTestCase.assertInHTML(needle, haystack, count=None, msg_prefix='')
 
-    Asserts that the HTML fragment ``needle`` is contained in the ``haystack`` one.
+    Asserts that the HTML fragment ``needle`` is contained in the ``haystack``
+    once.
 
     If the ``count`` integer argument is specified, then additionally the number
     of ``needle`` occurrences will be strictly verified.