diff --git a/src/calibre/ebooks/oeb/transforms/manglecase.py b/src/calibre/ebooks/oeb/transforms/manglecase.py
index 8ab6e14a98..762f72c237 100644
--- a/src/calibre/ebooks/oeb/transforms/manglecase.py
+++ b/src/calibre/ebooks/oeb/transforms/manglecase.py
@@ -82,7 +82,7 @@ class CaseMangler(object):
                 else:
                     last.tail = text
             else:
-                child = etree.Element(XHTML('span'), attrib=attrib)
+                child = elem.makeelement(XHTML('span'), attrib=attrib)
                 child.text = text.upper()
                 if last is None:
                     elem.insert(0, child)