BitVec::from_iter has unexpected len

[balopat]

Maybe I'm doing something wrong, but the code below is failing. I expected from_iter to result in a BitVec with the same len() as the number of iterated elements.

use bitvec::prelude::*;

fn main() {
    let bool_vec = vec![false, true];
    let bv: BitVec<usize, Lsb0> =
        BitVec::from_iter(
            bool_vec
                .iter()
                .map(|b| if *b { 1 as usize } else { 0 as usize }),
        );
    assert_eq!(bitvec![0, 1], bv);
}

failure:

thread 'main' panicked at src/main.rs:11:5:
assertion `left == right` failed
  left: BitVec<usize, bitvec::order::Lsb0> { addr: 0x5594c6db8bc0, head: 000000, bits: 2, capacity: 64 } [0, 1]
 right: BitVec<usize, bitvec::order::Lsb0> { addr: 0x5594c6db8ba0, head: 000000, bits: 128, capacity: 128 } [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
stack backtrace:
   0: rust_begin_unwind
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/std/src/panicking.rs:652:5
   1: core::panicking::panic_fmt
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/panicking.rs:72:14
   2: core::panicking::assert_failed_inner
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/panicking.rs:409:17
   3: core::panicking::assert_failed
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/panicking.rs:364:5
   4: temp::main
             at ./src/main.rs:11:5
   5: core::ops::function::FnOnce::call_once
             at /rustc/129f3b9964af4d4a709d1383930ade12dfe7c081/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.