diff --git a/tests/test_expt_class.py b/tests/test_expt_class.py
index 8cd6841f..6de6201b 100644
--- a/tests/test_expt_class.py
+++ b/tests/test_expt_class.py
@@ -112,7 +112,10 @@ def generate_temperature_arrays(nx, ny, number_vertical_layers):
     temp_in_C = np.random.randn(ny, nx, number_vertical_layers)
 
     temp_in_C_masked = np.copy(temp_in_C)
-    temp_in_C_masked[20:24, 32:35, :] = float("nan")
+    if int(ny/4+4) < ny-1 and int(nx/3+4) < nx+1:
+        temp_in_C_masked[int(ny/3):int(ny/3+5), int(nx):int(nx/4+4), :] = float("nan")
+    else:
+        raise ValueError("use bigger domain")
 
     temp_in_K = np.copy(temp_in_C) + 273.15
     temp_in_K_masked = np.copy(temp_in_C_masked) + 273.15