Get error message when assign mu with uniform distribution

New in Stan, if I replace “mu ~ normal(100, 20)” with “mu~uniform(80, 120)” I got error message in sampling method? Need help to understand why and how to fix that.

data {
  int nY;
  vector[nY] Y;

parameters {
  real mu;
  real sigma;

model {
    mu ~ normal(100, 20);
    sigma ~ normal(10, 50);
    Y ~ normal(mu, sigma);

I use pystan to practice stan. And I copy some error messages below :

RuntimeError Traceback (most recent call last)
1 out = sm.sampling(
----> 2 data = data

RuntimeError: Initialization failed.

You can specify a prior that is uniform on the interval [80, 120] by not defining any prior at all and just setting parameter bounds for mu . So in parameters block

real<lower=80,upper=120> mu;

Also, set real<lower=0> sigma;