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diff --git a/test-suite/bugs/closed/shouldsucceed/2021.v b/test-suite/bugs/closed/shouldsucceed/2021.v
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+++ b/test-suite/bugs/closed/shouldsucceed/2021.v
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+(* correct failure of injection/discriminate on types whose inductive
+   status derives from the substitution of an argument *)
+
+Inductive t : nat -> Type :=
+| M : forall n: nat, nat -> t n.
+
+Lemma eq_t : forall n n' m m',
+   existT (fun B : Type => B) (t n) (M n m) =
+   existT (fun B : Type => B) (t n') (M n' m') -> True.
+Proof.
+  intros.
+  injection H.
+  intro Ht.
+  exact I.
+Qed.
+
+Lemma eq_t' : forall n n' : nat,
+   existT (fun B : Type => B) (t n) (M n 0) =
+   existT (fun B : Type => B) (t n') (M n' 1) -> True.
+Proof.
+  intros.
+  discriminate H || exact I.
+Qed.