diff --git a/Examples/Tests/langmuir/inputs_test_3d_langmuir_multi_customcoef b/Examples/Tests/langmuir/inputs_test_3d_langmuir_multi_customcoef
index 1f78f24adc0..19808f536e1 100644
--- a/Examples/Tests/langmuir/inputs_test_3d_langmuir_multi_customcoef
+++ b/Examples/Tests/langmuir/inputs_test_3d_langmuir_multi_customcoef
@@ -3,3 +3,6 @@ FILE = inputs_base_3d
 
 algo.maxwell_solver = customcoef
 warpx.cfl = 0.5
+
+algo.custom_coef_upward_stencil_z = 0.5 0.1666666
+algo.custom_coef_downward_stencil_z = 0.5 0.1666666