diff --git a/src/calibre/ebooks/oeb/iterator.py b/src/calibre/ebooks/oeb/iterator.py
index 7912d26e83..3fdd6aaf99 100644
--- a/src/calibre/ebooks/oeb/iterator.py
+++ b/src/calibre/ebooks/oeb/iterator.py
@@ -166,7 +166,7 @@ class EbookIterator(object):
                         f.truncate()
                         f.write(ncss.encode(enc))
 
-    def __enter__(self, processed=False):
+    def __enter__(self, processed=False, only_input_plugin=False):
         self.delete_on_exit = []
         self._tdir = TemporaryDirectory('_ebook_iter')
         self.base  = self._tdir.__enter__()
@@ -184,12 +184,14 @@ class EbookIterator(object):
                 plumber.opts, plumber.input_fmt, self.log,
                 {}, self.base)
 
-        if processed or plumber.input_fmt.lower() in ('pdb', 'pdf', 'rb') and \
-                not hasattr(self.pathtoopf, 'manifest'):
-            if hasattr(self.pathtoopf, 'manifest'):
-                self.pathtoopf = write_oebbook(self.pathtoopf, self.base)
-            self.pathtoopf = create_oebbook(self.log, self.pathtoopf, plumber.opts,
-                    plumber.input_plugin)
+        if not only_input_plugin:
+            if processed or plumber.input_fmt.lower() in ('pdb', 'pdf', 'rb') and \
+                    not hasattr(self.pathtoopf, 'manifest'):
+                if hasattr(self.pathtoopf, 'manifest'):
+                    self.pathtoopf = write_oebbook(self.pathtoopf, self.base)
+                self.pathtoopf = create_oebbook(self.log, self.pathtoopf, plumber.opts,
+                        plumber.input_plugin)
+
         if hasattr(self.pathtoopf, 'manifest'):
             self.pathtoopf = write_oebbook(self.pathtoopf, self.base)
 
diff --git a/src/calibre/gui2/convert/regex_builder.py b/src/calibre/gui2/convert/regex_builder.py
index 8d00de2fe8..58e1d1ae45 100644
--- a/src/calibre/gui2/convert/regex_builder.py
+++ b/src/calibre/gui2/convert/regex_builder.py
@@ -85,7 +85,7 @@ class RegexBuilder(QDialog, Ui_RegexBuilder):
 
     def open_book(self, pathtoebook):
         self.iterator = EbookIterator(pathtoebook)
-        self.iterator.__enter__(processed=True)
+        self.iterator.__enter__(only_input_plugin=True)
         text = [u'']
         for path in self.iterator.spine:
             html = open(path, 'rb').read().decode('utf-8', 'replace')