condition in .xinitrc not satisfied, don't know why

I have a condition in .xinitrc that is not met, and I don't understand why: I have the .Xresources file in my ~ (with read permissions), and my ~/.xinitrc contains a line with [[ -f ~/.Xresources ]] && xrdb -load ~/.Xresources & However the condition between double brackets is not met. Why is that? The file exists and is located in my home! If I change the line to this, xrdb -load ~/.Xresources & Then it works, and also works if I run [[ -f ~/.Xresources ]] && xrdb -load ~/.Xresources from bash. Why is not working in .xinitrc? My solution for the moment was to put directly the second line, however I don't understand why the condition is not met.