Can't put some files into the QT Creator "Other files" folder

Unable to put a source file called "Example.yacc" into the "Other files" folder.

Adding the file via the Projects window, right clicking "Other files" ... "Add Existing Files..."  does get the file added into the project, but it comes in under "Headers".

I would have thought that only files with ".h" and\or perhaps ".hpp" would reside in the headers folder, and any other file extension would go into "Other files".