--- mechanize/_html.py
+++ mechanize/_html.py
@@ -621,6 +621,7 @@
         Factory.set_response(self, response)
         if response is not None:
             data = response.read()
+            response.seek(0)
             soup = self._soup_class(self.encoding, data)
             self._forms_factory.set_response(
                 copy.copy(response), self.encoding)