diff --git a/iris_heap_lang/derived_laws.v b/iris_heap_lang/derived_laws.v
index a6029e8719d1d365a79185c1f349f34bbe301e3b..7e28862f3adb9e87b9c302e47bbc1db6bee49eab 100644
--- a/iris_heap_lang/derived_laws.v
+++ b/iris_heap_lang/derived_laws.v
@@ -207,40 +207,32 @@ Qed.
 
 Lemma twp_xchg_offset s E l off vs v v' :
   vs !! off = Some v →
-  val_is_unboxed v →
-  val_is_unboxed v' →
   [[{ l ↦∗ vs }]] Xchg #(l +ₗ off) v' @ s; E [[{ RET v; l ↦∗ <[off:=v']> vs }]].
 Proof.
-  iIntros (Hlookup Hunboxed Hunboxed' Φ) "Hl HΦ".
+  iIntros (Hlookup Φ) "Hl HΦ".
   iDestruct (update_array l _ _ _ _ Hlookup with "Hl") as "[Hl1 Hl2]".
   iApply (twp_xchg with "Hl1") => //. iIntros "Hl1".
   iApply "HΦ". iApply "Hl2". iApply "Hl1".
 Qed.
 Lemma wp_xchg_offset s E l off vs v v' :
   vs !! off = Some v →
-  val_is_unboxed v →
-  val_is_unboxed v' →
   {{{ ▷ l ↦∗ vs }}} Xchg #(l +ₗ off) v' @ s; E {{{ RET v; l ↦∗ <[off:=v']> vs }}}.
 Proof.
-  iIntros (? ? ? Φ) ">H HΦ". iApply (twp_wp_step with "HΦ").
+  iIntros (? Φ) ">H HΦ". iApply (twp_wp_step with "HΦ").
   iApply (twp_xchg_offset with "H"); [eauto..|]; iIntros "H HΦ". by iApply "HΦ".
 Qed.
 
 Lemma twp_xchg_offset_vec s E l sz (off : fin sz) (vs : vec val sz) v :
-   val_is_unboxed (vs !!! off) →
-   val_is_unboxed v →
   [[{ l ↦∗ vs }]] Xchg #(l +ₗ off) v @ s; E [[{ RET (vs !!! off); l ↦∗ vinsert off v vs }]].
 Proof.
-  intros ? ?. setoid_rewrite vec_to_list_insert. apply twp_xchg_offset => //.
+  setoid_rewrite vec_to_list_insert. apply twp_xchg_offset => //.
   by apply vlookup_lookup.
 Qed.
 
 Lemma wp_xchg_offset_vec s E l sz (off : fin sz) (vs : vec val sz) v :
-   val_is_unboxed (vs !!! off) →
-   val_is_unboxed v →
-  {{{ ▷ l ↦∗ vs }}} Xchg #(l +ₗ off) v @ s; E {{{ RET (vs !!! off); l ↦∗ vinsert off v vs }}}.
+   {{{ ▷ l ↦∗ vs }}} Xchg #(l +ₗ off) v @ s; E {{{ RET (vs !!! off); l ↦∗ vinsert off v vs }}}.
 Proof.
-  iIntros (? ? Φ) ">H HΦ". iApply (twp_wp_step with "HΦ").
+  iIntros (Φ) ">H HΦ". iApply (twp_wp_step with "HΦ").
   iApply (twp_xchg_offset_vec with "H"); [eauto..|]; iIntros "H HΦ". by iApply "HΦ".
 Qed.
 
diff --git a/iris_heap_lang/lang.v b/iris_heap_lang/lang.v
index 6a69cb3413c471f518b6e6df7942489206ea2fae..f435cb81c792230cadb7fe30e5e8013bb590bcdc 100644
--- a/iris_heap_lang/lang.v
+++ b/iris_heap_lang/lang.v
@@ -684,8 +684,6 @@ Inductive head_step : expr → state → list observation → expr → state →
                []
   | XchgS l v1 v2 σ :
      σ.(heap) !! l = Some $ Some v1 →
-     val_is_unboxed v1 →
-     val_is_unboxed v2 →
      head_step (Xchg (Val $ LitV $ LitLoc l) (Val v2)) σ
                []
                (Val v1) (state_upd_heap <[l:=Some v2]> σ)
diff --git a/iris_heap_lang/primitive_laws.v b/iris_heap_lang/primitive_laws.v
index dffccaa399d8169c468d1c5390b54b44e38a0fb8..9b3510038a68406d9a226c5d82c8ab18a1c072ce 100644
--- a/iris_heap_lang/primitive_laws.v
+++ b/iris_heap_lang/primitive_laws.v
@@ -313,12 +313,10 @@ Proof.
 Qed.
 
 Lemma twp_xchg s E l v' v :
-  val_is_unboxed v →
-  val_is_unboxed v' →
   [[{ l ↦ v' }]] Xchg (Val $ LitV $ LitLoc l) (Val v) @ s; E
   [[{ RET v'; l ↦ v }]].
 Proof.
-  iIntros (Hv Hv' Φ) "Hl HΦ". iApply twp_lift_atomic_head_step_no_fork; first done.
+  iIntros (Φ) "Hl HΦ". iApply twp_lift_atomic_head_step_no_fork; first done.
   iIntros (σ1 κs n) "[Hσ Hκs] !>". iDestruct (gen_heap_valid with "Hσ Hl") as %?.
   iSplit; first by eauto with head_step.
   iIntros (κ v2 σ2 efs Hstep); inv_head_step.
@@ -327,12 +325,10 @@ Proof.
 Qed.
 
 Lemma wp_xchg s E l v' v :
-  val_is_unboxed v →
-  val_is_unboxed v' →
   {{{ ▷ l ↦ v' }}} Xchg (Val $ LitV (LitLoc l)) (Val v) @ s; E
   {{{ RET v'; l ↦ v }}}.
 Proof.
-  iIntros (Hv Hv' Φ) ">H HΦ". iApply (twp_wp_step with "HΦ").
+  iIntros (Φ) ">H HΦ". iApply (twp_wp_step with "HΦ").
   iApply (twp_xchg with "H"); [by auto..|]. iIntros "H HΦ". by iApply "HΦ".
 Qed.
 
diff --git a/iris_heap_lang/proofmode.v b/iris_heap_lang/proofmode.v
index ab18be35d326efad2999511b6bc0ec4b91492e34..5281421337e57053fbb0411bfddc994c20778003 100644
--- a/iris_heap_lang/proofmode.v
+++ b/iris_heap_lang/proofmode.v
@@ -373,15 +373,13 @@ Qed.
 Lemma tac_wp_xchg Δ Δ' s E i K l v v' Φ :
   MaybeIntoLaterNEnvs 1 Δ Δ' →
   envs_lookup i Δ' = Some (false, l ↦ v)%I →
-  val_is_unboxed v' →
-  val_is_unboxed v  →
   match envs_simple_replace i false (Esnoc Enil i (l ↦ v')) Δ' with
   | Some Δ'' => envs_entails Δ'' (WP fill K (Val $ v) @ s; E {{ Φ }})
   | None => False
   end →
   envs_entails Δ (WP fill K (Xchg (LitV l) (Val v')) @ s; E {{ Φ }}).
 Proof.
-  rewrite envs_entails_eq=> ?????.
+  rewrite envs_entails_eq=> ???.
   destruct (envs_simple_replace _ _ _) as [Δ''|] eqn:HΔ''; [ | contradiction ].
   rewrite -wp_bind. eapply wand_apply; first by eapply wp_xchg.
   rewrite into_laterN_env_sound -later_sep envs_simple_replace_sound //; simpl.
@@ -390,8 +388,6 @@ Proof.
 Qed.
 Lemma tac_twp_xchg Δ s E i K l v v' Φ :
   envs_lookup i Δ = Some (false, l ↦ v)%I →
-  val_is_unboxed v' →
-  val_is_unboxed v →
   match envs_simple_replace i false (Esnoc Enil i (l ↦ v')) Δ with
   | Some Δ' => envs_entails Δ' (WP fill K (Val $ v) @ s; E [{ Φ }])
   | None => False
diff --git a/iris_heap_lang/proph_erasure.v b/iris_heap_lang/proph_erasure.v
index 8ea48fb209593db102a107de9578f31b019da8de..8d96b7b0050f30faf7a52fcabced727c2360809f 100644
--- a/iris_heap_lang/proph_erasure.v
+++ b/iris_heap_lang/proph_erasure.v
@@ -279,16 +279,13 @@ Proof.
   eexists _, _, _, _; simpl; split; first econstructor; eauto.
 Qed.
 Lemma erased_head_step_head_step_Xchg l v w σ :
-  val_is_unboxed v →
-  val_is_unboxed w →
   erase_heap (heap σ) !! l = Some (Some v) →
   head_steps_to_erasure_of (Xchg #l w) σ v
    {| heap := <[l:=Some $ erase_val w]> (erase_heap (heap σ)); used_proph_id := ∅ |} [].
 Proof.
-  intros Hv Hw Hl.
+  intros Hl.
   rewrite lookup_erase_heap in Hl.
   destruct (heap σ !! l) as [[|]|] eqn:?; simplify_eq/=.
-  rewrite val_is_unboxed_erased in Hv * => //; intros Hv.
   eexists _, _, _, _; simpl; split; first econstructor; repeat split; eauto.
   rewrite /state_upd_heap /erase_state /= erase_heap_insert_Some //.
 Qed.
@@ -725,14 +722,11 @@ Proof.
 Qed.
 
 Lemma head_step_erased_prim_step_xchg σ l v w :
-  val_is_unboxed v →
-  val_is_unboxed w →
   heap σ !! l = Some (Some v) →
   ∃ e2' σ2' ef', prim_step (Xchg #l (erase_val w)) (erase_state σ) [] e2' σ2' ef'.
 Proof.
-  intros Hv Hw Hl. do 3 eexists; apply head_prim_step; econstructor.
-  1: rewrite /erase_state /state_upd_heap /= lookup_erase_heap Hl; eauto.
-  1,2: by rewrite val_is_unboxed_erased.
+  intros Hl. do 3 eexists; apply head_prim_step; econstructor.
+  rewrite /erase_state /state_upd_heap /= lookup_erase_heap Hl; eauto.
 Qed.
 
 Lemma head_step_erased_prim_step_store σ l v w :