diff --git a/scripts/prepare_sector_network.py b/scripts/prepare_sector_network.py
index 3e3e117c..9d099e07 100644
--- a/scripts/prepare_sector_network.py
+++ b/scripts/prepare_sector_network.py
@@ -2324,8 +2324,7 @@ def add_biomass(n, costs):
     if (
         options["municipal_solid_waste"]
         and not options["industry"]
-        and cf_industry["waste_to_energy"]
-        or cf_industry["waste_to_energy_cc"]
+        and (cf_industry["waste_to_energy"] or cf_industry["waste_to_energy_cc"])
     ):
         logger.warning(
             "Flag municipal_solid_waste can be only used with industry "