diff --git a/src/cal_tools/calcat_interface2.py b/src/cal_tools/calcat_interface2.py
index 5b0b827e4d09893b9a708028fb4f3f9ede5a88f2..ceb9751b706da0f8e458a3d728fbce4e77440f9d 100644
--- a/src/cal_tools/calcat_interface2.py
+++ b/src/cal_tools/calcat_interface2.py
@@ -325,6 +325,7 @@ class CalibrationData(Mapping):
             dset.read_direct(res[cal_type][mod])
 
         const_load_mp.map(_load_constant_dataset, keys)
+        return res
 
 
 class ConditionsBase: