diff --git a/src/cardiac_geometries/fibers/_lv_ellipsoid.py b/src/cardiac_geometries/fibers/_lv_ellipsoid.py
index 919b148..7f0ac47 100644
--- a/src/cardiac_geometries/fibers/_lv_ellipsoid.py
+++ b/src/cardiac_geometries/fibers/_lv_ellipsoid.py
@@ -17,7 +17,6 @@ def laplace(
     markers: Dict[str, Tuple[int, int]],
     function_space: str = "P_1",
 ):
-
     endo_marker = markers["ENDO"][0]
     epi_marker = markers["EPI"][0]
 
@@ -152,12 +151,12 @@ def compute_system(
     f0 = np.sin(al) * e_mu + np.cos(al) * e_theta
     f0 = normalize(f0)
 
-    s0 = np.cross(e_mu, e_theta, axis=0)
-    s0 = normalize(s0)
-
-    n0 = np.cross(f0, s0, axis=0)
+    n0 = np.cross(e_mu, e_theta, axis=0)
     n0 = normalize(n0)
 
+    s0 = np.cross(f0, n0, axis=0)
+    s0 = normalize(s0)
+
     Vv = dolfin.FunctionSpace(
         mesh,
         dolfin.VectorElement(
@@ -227,7 +226,6 @@ def create_microstructure(
     function_space,
     outdir: Optional[Union[str, Path]] = None,
 ) -> Microstructure:
-
     t = laplace(mesh, ffun, markers, function_space=function_space)
     system = compute_system(
         t,