diff --git a/carsus/io/output/base.py b/carsus/io/output/base.py
index 21846df66..017701d0d 100644
--- a/carsus/io/output/base.py
+++ b/carsus/io/output/base.py
@@ -196,8 +196,8 @@ def to_hdf(self, fname):
             "/molecules/ionization_energies": (self.barklem_2016_data, "ionization_energies"),
             "/molecules/dissociation_energies": (self.barklem_2016_data, "dissociation_energies"),
             "/molecules/partition_functions": (self.barklem_2016_data, "partition_functions"),
-            "/collisions_data": (self.collisions_preparer, "collisions_prepared"),
-            "/collisions_metadata": (self.collisions_preparer, "collisions_metadata"),
+            "/collisions_data": (self, "collisions_prepared"),
+            "/collisions_metadata": (self, "collisions_metadata"),
             "/photoionization_data": (self.cross_sections_preparer, "cross_sections_prepared"),
         }