MATLAB: Tf multiplication not working

The example code works fine on my 2014b version but does not work on 2016b:

    s = tf('s');
    G = s/(s+1);

Outputs are (2014b:)

G =
    s
  -----
  s + 1
Continuous-time transfer function.

2016b:

Undefined operator '+' for input arguments of type 'tf'.

the "ver" command confirms the proper availability of the control toolbox:

Control System Toolbox                                Version 10.1

The "which tf" command returns the following (2016b):

C:\Program Files\MATLAB\R2016b\toolbox\control\ctrlmodels\@tf\tf.m  % tf constructor

What is wrong?