sym('do') or 'syms do' fails

Both of these fail in MATLAB R2012a and MATLAB R2010b:

syms do
sym('do')

The error message in R2010b is:

>> syms do
??? Error using ==> mupadmex
Error in MuPAD command: Unexpected 'do' [line 1, col 18]

Error in ==> sym.sym>convertName at 2496
    s = mupadmex('symobj::fixupVar',x,0);

Error in ==> sym.sym>convertChar at 2424
    s = convertName(x);

Error in ==> sym.sym>convertCharWithOption at 2410
        s = convertChar(x);

Error in ==> sym.sym>tomupad at 2164
        S = convertCharWithOption(x,a);

Error in ==> sym.sym>sym.sym at 111
                S.s = tomupad(x,'');

Error in ==> syms at 77
      assignin('caller',x,sym(x));

>> sym('do')
??? Error using ==> mupadmex
Error in MuPAD command: Unexpected 'do' [line 1, col 18]

Error in ==> sym.sym>convertName at 2496
    s = mupadmex('symobj::fixupVar',x,0);

Error in ==> sym.sym>convertChar at 2424
    s = convertName(x);

Error in ==> sym.sym>convertCharWithOption at 2410
        s = convertChar(x);

Error in ==> sym.sym>tomupad at 2164
        S = convertCharWithOption(x,a);

Error in ==> sym.sym>sym.sym at 111
                S.s = tomupad(x,'');

Am I doing something wrong or is this expected behavior?