BugFix - _cls not set in constructor #1950

mongoengine/base/document.py

@@ -91,6 +91,9 @@ class BaseDocument(object):
             value = getattr(self, key, None)
             setattr(self, key, value)
 
+        if '_cls' not in values:
+            self._cls = self._class_name
+
         # Set passed values after initialisation
         if self._dynamic:
             dynamic_data = {}