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diff --git a/test-suite/bugs/closed/bug_12571.v b/test-suite/bugs/closed/bug_12571.v
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+Axiom IsTrunc : Type -> Type.
+
+Existing Class IsTrunc.
+
+Declare Instance trunc_forall :
+  forall (A : Type) (P : A -> Type),
+  IsTrunc (forall a : A, P a).
+
+Axiom Graph : Set.
+Axiom in_N : forall (n : Graph), Type.
+
+Definition N : Type := @sigT Graph in_N.
+
+Goal forall (P : N -> Type)
+ (Q := fun m : Graph => forall mrec : in_N m, P (existT _ m mrec))
+ (A : Graph), IsTrunc (Q A).
+Proof.
+intros.
+solve [typeclasses eauto].
+Qed.