diff --git a/Examples/Waveguide/inputs_3d_empty_X_band b/Examples/Waveguide/inputs_3d_empty_X_band
index 7d7dc6b63..5d4ecec41 100644
--- a/Examples/Waveguide/inputs_3d_empty_X_band
+++ b/Examples/Waveguide/inputs_3d_empty_X_band
@@ -8,7 +8,7 @@
 ####### GENERAL PARAMETERS ######
 #################################
 max_step = 1000000
-amr.n_cell = 512 4 512 # number of cells spanning the domain in each coordinate direction at level 0
+amr.n_cell = 128 4 128 # number of cells spanning the domain in each coordinate direction at level 0
 amr.max_grid_size = 64 # maximum size of each AMReX box, used to decompose the domain
 amr.blocking_factor = 4 # only meaningful for AMR
 geometry.dims = 3