rhai: Cannot create recursive function in module

Seems like I cannot create a recursive function inside a module.

extern crate rhai;

use rhai::{Engine, Module, Scope};

const MODULE_TEXT: &str = r#"
fn factorial(n) {
    if n == 1 {
        return 1;
    } else {
        return factorial(n-1);
    }
}
"#;

const SCRIPT: &str = r#"
    import "test_module" as test;
    print(test::factorial(5));
"#;

fn main() {
    let mut engine = Engine::new();
    let module_ast = engine.compile(MODULE_TEXT).unwrap();
    let module = Module::eval_ast_as_new(Scope::new(), &module_ast, &engine).unwrap();
    let mut static_modules = rhai::module_resolvers::StaticModuleResolver::new();
    static_modules.insert("test_module", module);
    engine.set_module_resolver(Some(static_modules));

    engine.consume(SCRIPT).unwrap();
}

Results in: ErrorInFunctionCall("factorial", ErrorFunctionNotFound("factorial (i64)", 6:16), 3:17)

Upon further testing, it also looks like I cannot access other functions defined in the same module either, even though I expect all of those to be in scope. Am I misunderstanding something, or is this a bug?