diff --git a/pybamm/discretisations/discretisation.py b/pybamm/discretisations/discretisation.py
index 48681b3f1d..abace025f3 100644
--- a/pybamm/discretisations/discretisation.py
+++ b/pybamm/discretisations/discretisation.py
@@ -994,7 +994,9 @@ def check_initial_conditions(self, model):
         """Check initial conditions are a numpy array"""
         # Individual
         for var, eqn in model.initial_conditions.items():
-            assert type(eqn.evaluate(t=0, u="shape test")) is np.ndarray, pybamm.ModelError(
+            assert (
+                type(eqn.evaluate(t=0, u="shape test")) is np.ndarray
+            ), pybamm.ModelError(
                 """
                 initial_conditions must be numpy array after discretisation but they are
                 {} for variable '{}'.