diff --git a/examples/find-photonic-mode-sk.py b/examples/find-photonic-mode-sk.py
index ef670801c0e02da4feb62f5c31760b4cc69f0ead..a818ffe104884a9ead057a72ad52b65e09a8f05c 100644
--- a/examples/find-photonic-mode-sk.py
+++ b/examples/find-photonic-mode-sk.py
@@ -81,7 +81,7 @@ 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 967b2d33ef12e78fa163528ca5ce0936f620f8bb..6a303570d853cd0c9203fa66c930b5000efd5bfd 100644
--- a/pytential/symbolic/pde/maxwell/waveguide.py
+++ b/pytential/symbolic/pde/maxwell/waveguide.py
@@ -329,9 +329,9 @@ class SecondKindInfZMuellerOperator(L2WeightedPDEOperator):
                         1j * (Tt(where, dom0i, phi) - Tt(where, dom1i, phi))
                         - 1j * (
                             n0**2 * tangent.scalar_product(
-                                S(dom0i, normal * phi))
+                                S(dom0i, tangent * phi))
                             - n1**2 * tangent.scalar_product(
-                                S(dom1i, normal * phi))))
+                                S(dom1i, tangent * phi))))
 
             a23 = +1*sym.cse(a23_expr(phi3), "a23")
             a41 = -1*sym.cse(a23_expr(phi1), "a41")