diff --git a/pybis/src/python/pybis/definitions.py b/pybis/src/python/pybis/definitions.py
index 0cd08014e584795b8131aac953b62fe69307458c..3136f86e3af3eb4eb1edb83e4d073a40ea5ec852 100644
--- a/pybis/src/python/pybis/definitions.py
+++ b/pybis/src/python/pybis/definitions.py
@@ -1,3 +1,6 @@
+import copy
+
+
 def openbis_definitions(entity):
     """
     attrs_new: Attributes, that can appear when creating new entities
@@ -454,7 +457,7 @@ fetch_option = {
 def get_fetchoption_for_entity(entity):
     entity = entity[0].lower() + entity[1:]  # make first character lowercase
     try:
-        return fetch_option[entity]
+        return copy.deepcopy(fetch_option[entity])
     except KeyError as e:
         return {}