# Error code E0384

An immutable variable was reassigned.

Erroneous code example:

    fn main() {
        let x = 3;
        x = 5; // error, reassignment of immutable variable
    }

By default, variables in Rust are immutable. To fix this error, add the keyword `mut` after the keyword `let` when declaring the variable. For example:

    fn main() {
        let mut x = 3;
        x = 5;
    }

Alternatively, you might consider initializing a new variable: either with a new bound name or (by shadowing) with the bound name of your existing variable. For example:

    fn main() {
        let x = 3;
        let x = 5;
    }