diff --git a/cobrakbase/core/kbasefba/fbamodel_reaction.py b/cobrakbase/core/kbasefba/fbamodel_reaction.py
index 44f8dfd..12b3153 100755
--- a/cobrakbase/core/kbasefba/fbamodel_reaction.py
+++ b/cobrakbase/core/kbasefba/fbamodel_reaction.py
@@ -302,7 +302,7 @@ def _to_json(self):
                                 "~/genome/features/id/" + x
                                 for x in complex_group.notes[
                                     f"complex_subunit_features_{su}"
-                                ].split(";")
+                                ].split(";") if x
                             ],
                         }
                         model_reaction_protein["modelReactionProteinSubunits"].append(