Solve App and Piecewise function

[cclinus]

Hello,

I try to solve two equations in Solve App.
E1: E=C MOD 5
E2: F=PIECEWISE(E not equal 0,E,E==0,5)
   
Then in Num view, uncheck C and enter C=5 and press Solve.
The answer of E is 0, OK
But, the answer of F is also 0, Wrong.
F is supposed to be 5.
   
Did I do anything wrong?