diff --git a/src/calibre/test_build.py b/src/calibre/test_build.py
index e9ade03cda..3ec022eb3f 100644
--- a/src/calibre/test_build.py
+++ b/src/calibre/test_build.py
@@ -48,6 +48,9 @@ class BuildTest(unittest.TestCase):
     def test_html5lib(self):
         import html5lib.html5parser  # noqa
         from html5lib import parse  # noqa
+        # Test that we are using the calibre version of html5lib
+        from calibre.ebooks.oeb.polish.parsing import parse_html5
+        parse_html5('<p>xxx')
 
     def test_spell(self):
         from calibre.spell.dictionary import test_dictionaries