[Help-glpk] dual values

[name name]

Hello,

I'm adding a column in a model and when I calculate the dual values I got wrong results

Minimize
 objective: + 6 x_1 + x_2 + x_3 + 5 x_4 + 2 x_5 + 7 x_6 + 7 x_7 + 6 x_8
 + 3 x_9 + 3 x_10 + 7 x_11 + 8 x_12 + 8 x_13 + 2 x_14 + 5 x_15

Subject To
 constraint1: + x_1 = 1
 constraint2: + x_2 = 1
 constraint3: + x_3 = 1
 constraint4: + x_4 = 1
 constraint5: + x_5 = 1
 constraint6: + x_6 = 1
 constraint7: + x_7 + x_16 = 1
 constraint8: + x_8 = 1
 constraint9: + x_9 = 1
 constraint10: + x_10 = 1
 constraint11: + x_16 + x_11 = 1
 constraint12: + x_16 + x_12 = 1
 constraint13: + x_13 + x_16 = 1
 constraint14: + x_14 = 1
 constraint15: + x_15 = 1

End

I have added x-16.
Shouldn't the dual for the variables x_7, x_11 , x_12 and x_13 be equal to 0 ?

Thank you

Onor