Combining shapes doesn't work in PowerPoint

Question

I've added Combine Shapes to my ribbon, as per this article on the MS Office blog.

I select the first shape, the second shape and... it remains inactive. Disabled.

When drawing new shapes, it works fine and I can combine shapes, intersect them and so on.

What gives?

Solution

Well, apparently, combining a shape only works when its text is empty. After deleting the text, everything worked fine. After combining I added the text back.