GA/simulink optimisation error

Hello,

Whe using pattern search for sdo optimise and changing the options for GA using gaoptimset, I get the following error:

Error using sdo.optimize (line 130)
SWITCH expression must be a scalar or string constant.

My code is:

opt = sdo.OptimizeOptions;
opt.Method = 'patternsearch'; 
opt.UseParallel ='always'; 
opt.MethodOptions=gaoptimset('Generations',20,'UseParallel',1,'PlotFcn',@gaplotbestf); 

I am using MATLAB 2015b. Can anyone direct me where I have gone wrong?

THank you.