Hi This is interesting, because i have 2 different places in which i install Qt, one in /opt in another in /home/daniel, some programs refere to one library place (/home/daniel/Qt/5.5/gcc_64/lib) and "designer" refere to /opt/Qt/5.5/gcc_64/lib. I not need to set LD_LIBRARY_PATH. After copy this one file to /opt/Qt/5.5/gcc_64/lib, "designer" also works. Daniel