diff --git a/etrago/tools/utilities.py b/etrago/tools/utilities.py
index dc66d232..ebc858f1 100755
--- a/etrago/tools/utilities.py
+++ b/etrago/tools/utilities.py
@@ -127,8 +127,16 @@ def buses_grid_linked(network, voltage_level):
     mask = (
         network.buses.index.isin(network.lines.bus0)
         | (network.buses.index.isin(network.lines.bus1))
-        | (network.buses.index.isin(network.links.loc[network.links.carrier=="DC", "bus0"]))
-        | (network.buses.index.isin(network.links.loc[network.links.carrier=="DC", "bus1"]))
+        | (
+            network.buses.index.isin(
+                network.links.loc[network.links.carrier == "DC", "bus0"]
+            )
+        )
+        | (
+            network.buses.index.isin(
+                network.links.loc[network.links.carrier == "DC", "bus1"]
+            )
+        )
     ) & (network.buses.v_nom.isin(voltage_level))
 
     df = network.buses[mask]