tmux and text selection with mouse through putty

I'm running tmux in a putty session. Normally(running just a plain shell or GNU Screen) to select text I'd just left click and drag the mouse across some text.

With tmux, I have to hold shift while selecting text with a mouse. How can I get the "normal" behavior back

Edit, this seems to be caused by "set-option mouse-select-pane on" in tmux. So, is there any way I can keep "set-option mouse-select-pane on", and still be able to select text without pressing "Shift" ?

No. In order to implement mouse-select-pane, tmux must capture the mouse from the terminal (like any other terminal application which supports the mouse). In most terminals, including putty, this means you need to use shift for standard copy and paste. It is impossible to have both mouse-select-pane and the putty clipboard work without shift.

However, the latest development tmux (in the Subversion repository) support using the mouse to copy directly into tmux paste buffer (with the mode-mouse option turned on). It also supports syncing with the terminal clipboard on some terminals (xterm at least, although I'm not sure about putty).