diff --git a/src/atomate2/forcefields/flows/phonons.py b/src/atomate2/forcefields/flows/phonons.py
index cadcad884f..254c30244a 100644
--- a/src/atomate2/forcefields/flows/phonons.py
+++ b/src/atomate2/forcefields/flows/phonons.py
@@ -129,7 +129,9 @@ class PhononMaker(Maker):
     prefer_90_degrees: bool = True
     get_supercell_size_kwargs: dict = field(default_factory=dict)
     use_symmetrized_structure: str | None = None
-    bulk_relax_maker: BaseVaspMaker | None = field(default_factory=lambda: CHGNetRelaxMaker(relax_kwargs={"fmax":0.0005}))
+    bulk_relax_maker: BaseVaspMaker | None = field(
+        default_factory=lambda: CHGNetRelaxMaker(relax_kwargs={"fmax": 0.0005})
+    )
     static_energy_maker: BaseVaspMaker | None = field(default_factory=CHGNetStaticMaker)
     phonon_displacement_maker: BaseVaspMaker = field(default_factory=CHGNetStaticMaker)
     create_thermal_displacements: bool = True