Find modulo for matlab

Hi,I want to find d from 7*d mod 40=1 , I do

 syms d
 eqn= 7*d==1;
 solve(eqn,d,Domain=Dom::IntegerMod(40))

But there error ,help me please

[Walter Roberson]

Duplicated by http://uk.mathworks.com/matlabcentral/answers/224275-i-find-d-from-7-d-mod-40-1