diff --git a/examples/find-photonic-mode-sk.py b/examples/find-photonic-mode-sk.py
index 0e65f3903f01445d5e1b669322ce9983b55e6760..ba52dffb8ab0cf170e02f9627606d7f078ff8e49 100644
--- a/examples/find-photonic-mode-sk.py
+++ b/examples/find-photonic-mode-sk.py
@@ -82,7 +82,7 @@ def find_mode():
     mesh = make_curve_mesh(curve_f,
             np.linspace(0, 1, nelements+1),
             target_order)
-    circle_radius = 50*k_vacuum
+    circle_radius = 4*k_vacuum
     mesh = affine_map(mesh, A=circle_radius*np.eye(2))
 
     from meshmode.discretization import Discretization
diff --git a/pytential/symbolic/pde/maxwell/waveguide.py b/pytential/symbolic/pde/maxwell/waveguide.py
index e417584e20fcf4646fd569127d88f952f42c3fba..aa86013d95dc2ae2a59713b5c808ff8d5dcc7503 100644
--- a/pytential/symbolic/pde/maxwell/waveguide.py
+++ b/pytential/symbolic/pde/maxwell/waveguide.py
@@ -227,9 +227,9 @@ class SecondKindInfZMuellerOperator(L2WeightedPDEOperator):
                         1j * (Tt(0, phi) - Tt(1, phi))
                         - 1j * (
                             n0**2 * tangent.scalar_product(
-                                S(0, normal * phi))
+                                S(0, tangent * phi))
                             - n1**2 * tangent.scalar_product(
-                                S(1, normal * phi))))
+                                S(1, tangent * phi))))
 
             a23 = +1*sym.cse(a23_expr(phi3), "a23")
             a41 = -1*sym.cse(a23_expr(phi1), "a41")