diff --git a/src/cal_tools/calcat_interface2.py b/src/cal_tools/calcat_interface2.py
index 6595057c0f48c945aa5f6f9b0d357318ae0daf34..ede5a89ca31222ed63cf10734d709f09885134a8 100644
--- a/src/cal_tools/calcat_interface2.py
+++ b/src/cal_tools/calcat_interface2.py
@@ -77,7 +77,7 @@ class ModulesConstantVersions:
     constants: Dict[str, SingleConstantVersion]  # Keys e.g. 'LPD00'
 
     def select_modules(self, *aggregators) -> "ModulesConstantVersions":
-        d = {aggr: scv for (aggr, scv) in self.constants if aggr in aggregators}
+        d = {aggr: scv for (aggr, scv) in self.constants.items() if aggr in aggregators}
         return ModulesConstantVersions(d)
 
     @property