diff --git a/examples/demo/advanced/data_cube.py b/examples/demo/advanced/data_cube.py
index 9420a783d..f2cc5f7cb 100644
--- a/examples/demo/advanced/data_cube.py
+++ b/examples/demo/advanced/data_cube.py
@@ -68,7 +68,7 @@ def __init__(self, *args, **kwargs):
         super(Model, self).__init__(*args, **kwargs)
         self.compute_model()
 
-    @on_trait_change("npts_+", "min_+", "max_+")
+    @on_trait_change("npts_+, min_+, max_+")
     def compute_model(self):
         def vfunc(x, y, z):
             return sin(x*z) * cos(y)*sin(z) + sin(0.5*z)