diff --git a/src/calibre/ebooks/oeb/iterator.py b/src/calibre/ebooks/oeb/iterator.py
index 33cc96f08b..05bbe7410d 100644
--- a/src/calibre/ebooks/oeb/iterator.py
+++ b/src/calibre/ebooks/oeb/iterator.py
@@ -122,7 +122,7 @@ class EbookIterator(object):
                                 else:
                                     print 'Loaded embedded font:', repr(family)
 
-    def __enter__(self):
+    def __enter__(self, raw_only=False):
         self.delete_on_exit = []
         self._tdir = TemporaryDirectory('_ebook_iter')
         self.base  = self._tdir.__enter__()
@@ -139,7 +139,7 @@ class EbookIterator(object):
                 plumber.opts, plumber.input_fmt, self.log,
                 {}, self.base)
 
-        if plumber.input_fmt.lower() in ('pdf', 'rb'):
+        if not raw_only and plumber.input_fmt.lower() in ('pdf', 'rb'):
             self.pathtoopf = create_oebbook(self.log, self.pathtoopf, plumber.opts,
                     plumber.input_plugin)
         if hasattr(self.pathtoopf, 'manifest'):
diff --git a/src/calibre/gui2/convert/regex_builder.py b/src/calibre/gui2/convert/regex_builder.py
index 0ef4f29202..20da8d7aaf 100644
--- a/src/calibre/gui2/convert/regex_builder.py
+++ b/src/calibre/gui2/convert/regex_builder.py
@@ -87,7 +87,7 @@ class RegexBuilder(QDialog, Ui_RegexBuilder):
 
     def open_book(self, pathtoebook):
         self.iterator = EbookIterator(pathtoebook)
-        self.iterator.__enter__()
+        self.iterator.__enter__(raw_only=True)
         text = [u'']
         for path in self.iterator.spine:
             html = open(path, 'rb').read().decode(path.encoding, 'replace')