diff --git a/differt2d/geometry.py b/differt2d/geometry.py
index 47a12b0..55b33da 100644
--- a/differt2d/geometry.py
+++ b/differt2d/geometry.py
@@ -526,7 +526,7 @@ class RIS(Wall, eqx.Module):
     with respect to its normal, regardless of the incident vector.
     """
 
-    phi: Float[Array, " "] = eqx.field(default_factory=jnp.array(jnp.pi / 4))
+    phi: Float[Array, " "] = eqx.field(default_factory=lambda: jnp.array(jnp.pi / 4))
     """The constant angle of reflection."""
 
     @jax.jit
@@ -689,7 +689,9 @@ def intersects_with_objects(
         :return: Whether this path intersects any of the objects, ().
         """
         interacting_object_indices = [-1] + [i for i in path_candidate] + [-1]
-        intersects = false_value(approx=approx)  # TODO(fixme): wtf this is a NumPy array?
+        intersects = false_value(
+            approx=approx
+        )  # TODO(fixme): wtf this is a NumPy array?
 
         for i in range(self.points.shape[0] - 1):
             ray_path = self.points[i : i + 2, :]