diff --git a/tests/test_generalized_raking.py b/tests/test_generalized_raking.py
index ba3c5c9..ec93fc7 100644
--- a/tests/test_generalized_raking.py
+++ b/tests/test_generalized_raking.py
@@ -38,7 +38,10 @@ def test_invalid_input():
         data = pd.DataFrame({"Gender": ["Male", "Male", "Female"]})
         raker = GeneralizedRaker({"Gender": {"Male": 0.51, "Female": 0.5}})
         raker.rake(data)
-    with pytest.raises(KeyError, match="There are observations for a value in 'Gender' that has not been mapped to a population target"):
+    with pytest.raises(
+        KeyError,
+        match="There are observations for a value in 'Gender' that has not been mapped to a population target",
+    ):
         data = pd.DataFrame({"Gender": ["Male", "Male", "Female", "Other"]})
         raker = GeneralizedRaker({"Gender": {"Male": 0.51, "Female": 0.49}})
         raker.rake(data)
diff --git a/weightfactors/raking/generalized_raker.py b/weightfactors/raking/generalized_raker.py
index 267ed50..21f0736 100644
--- a/weightfactors/raking/generalized_raker.py
+++ b/weightfactors/raking/generalized_raker.py
@@ -124,7 +124,9 @@ def validate_input(self, data: pd.DataFrame) -> None:
             # Make sure all unique values in the target columns have been mapped
             # It is impossible to set values with observations to a weight of 0
             if len(data[key].unique()) != len(value):
-                raise KeyError(f"There are observations for a value in '{key}' that has not been mapped to a population target")
+                raise KeyError(
+                    f"There are observations for a value in '{key}' that has not been mapped to a population target"
+                )
             # Make sure we have at least 1 observation for each category
             # It is impossible to set values without observations to a weight larger than 1
             for k, _ in value.items():