diff --git a/scripts/add_existing_baseyear.py b/scripts/add_existing_baseyear.py
index 15c57f32..d0f85a1a 100644
--- a/scripts/add_existing_baseyear.py
+++ b/scripts/add_existing_baseyear.py
@@ -552,7 +552,7 @@ def add_heating_capacities_installed_before_baseyear(
                 nodes,
                 suffix=f"{heat_system} gas boiler-{grouping_year}",
                 bus0="EU gas" if "EU gas" in spatial.gas.nodes else nodes + " gas",
-                bus1=f"{nodes}  {heat_system} heat",
+                bus1=nodes + " " + heat_system.value + " heat",
                 bus2="co2 atmosphere",
                 carrier=heat_system.value + " gas boiler",
                 efficiency=costs.at[heat_system.gas_boiler_costs_name, "efficiency"],
@@ -575,7 +575,7 @@ def add_heating_capacities_installed_before_baseyear(
                 nodes,
                 suffix=f" {heat_system} oil boiler-{grouping_year}",
                 bus0=spatial.oil.nodes,
-                bus1=f"{nodes}  {heat_system} heat",
+                bus1=nodes + " " + heat_system.value + " heat",
                 bus2="co2 atmosphere",
                 carrier=heat_system.value + " oil boiler",
                 efficiency=costs.at[heat_system.oil_boiler_costs_name, "efficiency"],