diff --git a/examples/api/custom_scale_example.py b/examples/api/custom_scale_example.py
index 92ca2a784373..df8fe46d2737 100644
--- a/examples/api/custom_scale_example.py
+++ b/examples/api/custom_scale_example.py
@@ -103,6 +103,7 @@ class MercatorLatitudeTransform(mtransforms.Transform):
         input_dims = 1
         output_dims = 1
         is_separable = True
+        has_inverse = True
 
         def __init__(self, thresh):
             mtransforms.Transform.__init__(self)
@@ -138,6 +139,7 @@ class InvertedMercatorLatitudeTransform(mtransforms.Transform):
         input_dims = 1
         output_dims = 1
         is_separable = True
+        has_inverse = True
 
         def __init__(self, thresh):
             mtransforms.Transform.__init__(self)