add-change-log-entry behaves different in different dir

Hello I am confused about the behaviour of the add-change-log-entry function. I have 2 files of the same type, say test.tex and test2.tex, in 2 different directories say foo1 and foo2. When I call this function say in a test.tex (in foo) or in test2.tex (in foo2) the following can happen - test.tex: I am asked to confirm the name of the changelog file, which is per default ~/ChangeLog - test2.tex: I am asked to confirm the name of the changelog file which is per default ~/foo2/ChangeLog (that is relative to the directory and this is the behaviour I want) This different behaviour has nothing to do whether the Changelog file exits already in the foo2 directory or not. It seems also to be independent of the directory or the file type. Per default I have set change-log-default-name to nil and more important add-log-file-name-function to nil as well since the documentation states ,---- | This function is called with one argument, the value of variable | `buffer-file-name' in that buffer. If this is nil, the default is to | use the file's name relative to the directory of the change log file. And all add-log-buffer-file-name-function' nil ,---- | Documentation: | *If non-nil, function to call to identify the full filename of a buffer. | This function is called with no argument. If this is nil, the default is to | use `buffer-file-name'. | `---- However when I call add-log-file-name-function it seems that the nil value is overwritten to ~/ChangeLog and I don't understand why. Can somebody help me please Thanks Uwe Brauer