Mouse tip for NIOS-II 12.0 SBT

I am using NIOS-II 12.0 SP2 SBT. In the debugger mode, when I move the mouse pointer over a variable, the value of the variable is not shown while NIOS-II IDE can show the value. Please tell me what option I should set to show the value of a variable in NIOS-II 12.0SP2 SBT. Thanks.