fdesign no longer working in version 2013b

I recently updated from R2011b to R2013b and now it seems I can no longer use the fdesign objects. I still have both versions installed. See example outputs below. Any ideas?

MATLAB R2011b:

>> H = fdesign.lowpass

H =

               Response: 'Lowpass'      
          Specification: 'Fp,Fst,Ap,Ast'
            Description: {4x1 cell}     
    NormalizedFrequency: true           
                  Fpass: 0.45           
                  Fstop: 0.55           
                  Apass: 1              
                  Astop: 60

MATLAB R2013b:

>> H = fdesign.lowpass

Warning: an error occurred while parsing class fdesign.lowpass: Undefined function or variable 'isfdtbxinstalled'.

Undefined function or variable 'fdesign.lowpass'.