diff --git a/src/caosdb/exceptions.py b/src/caosdb/exceptions.py
index 25dfe747843d5f09ab8a6076348b178281eed02c..5763bef4ac805a7dd1dfde8da2f6f3b7e5fd4bd8 100644
--- a/src/caosdb/exceptions.py
+++ b/src/caosdb/exceptions.py
@@ -278,7 +278,7 @@ class EntityError(TransactionError):
     def _convert(self):
         t = self._calc_bases()
         # TODO is it really a good idea to create dynamically types here?
-        newtype = type('EntityMultiError', t, {})
+        newtype = type('EntityMultiError', t+(Exception,), {})
         newinstance = newtype(error=self.error, entity=self.entity)
         setattr(newinstance, 'msg', self.msg)
         setattr(newinstance, 'errors', self.errors)