%spinfile-%

I use a macro %spinfile-<filename>% and get a different string every time, just like in a macro %spinfile2-<filename>%
For example, in article body:

%spinfile-file.txt%
%spinfile-file.txt%
%spinfile-file.txt%

gives:

random line 31
random line 55
random line 14

Wiki says: Though the same line is used if this macro is used more than once on a submission with the same file.
What am I doing wrong?