Cannot manage to change icon of Template Sheet folder

Somehow I cannot manage to change the icon of the Template Sheet folder. The .scrivx file however shows the entry for the custom icon:

<BinderItem ID="20" UUID="082B97F3-E03E-4398-BFFA-32C1E10D8EE5" Created="2010-10-20 10:57:18 +0200" Modified="2016-10-18 23:02:29 +0200" Type="Folder"> <Title>Template Sheets</Title> <MetaData> <IconFileName>aa_templates_blue.png</IconFileName> </MetaData>

But in the binder only the default icon appears. This is a different behavior from all other folders, even the standard ones like Draft, Research and Trash. Only if I use Clear Templates Folder, the custom icon is displayed. Once I set it back as Template Folder the default icon appears. Is this intended behavior?