I am porting some old proofs for 8.9 to 8.10.2 and immediately stumbled upon a problem. Consider this lemma:

```
Require Import CoLoR.Util.Vector.VecUtil.
Import VectorNotations.
Open Scope vector_scope.
Lemma Vbuild_1 B gen:
@Vbuild B 1 gen = [gen 0 (Arith.Lt.lt_0_Sn 0)].
Proof.
unfold Vbuild.
cbn.
apply Vcons_eq.
split.
- apply f_equal, Peano_dec.le_unique.
- reflexivity.
Qed.
```

After `cbn`

step in Coq-8.9 the goal looks like:

`[gen 0 (VecUtil.Vbuild_spec_obligation_4 gen eq_refl)] = [gen 0 (PeanoNat.Nat.lt_0_succ 0)]`

However, with Coq 8.10.2 I get:

eq_rect 1 (fun H : nat => vector B H)

[gen 0 (VecUtil.Vbuild_spec_obligation_4 eq_refl)] 1

(VecUtil.Vbuild_spec_obligation_5 eq_refl) = [gen 0 (PeanoNat.Nat.lt_0_succ 0)]

Any ideas why? What is the recommended way of dealing with this? Thanks!