Cody toolbox availability

I've been wondering whether toolbox functions are available in Cody. Alan Chalker set as a problem testing whether a given toolbox is available on the Cody server, and the results seem to show that the Image Processing Toolbox is available.

However, when I try to call imfilter, an IPT function, I get an error from Cody.

Here's my solution to the test problem:

function y = toolbox(x)
  v = ver;
  y = ismember(x, {v.Name});
  % double check that IPT is actually available
   imfilter(rand(5), rand(2));
end

and here's what comes back:

 Error: Undefined function 'imfilter' for input arguments of type 'double'.

If I omit the last line of my "solution", it works fine and appears to report that the IPT is available.

Has anyone any insight into this, please? I'm wondering if I'm doing something really stupid.