[Therion] symbol "u" problem

Hello, I don´t know what I am doing wrong, but if I use something like this in layout: symbol-hide line wall (or show, color, assign), everything works perfect. But, it doesn´t work with "u" , so symbol-hide line u:definedname will make an error with comment - unknown symbol specification. In layout there is a definition of u:definedname, as well as "initsymbol("l_u_definedname"); , outside layout is defined name for legend and everything works well, except symbol-hide (or so) command. Do you have any idea? Thank you Palo