diff --git a/tests/lean/phashmap_inst_coherence.lean b/tests/lean/phashmap_inst_coherence.lean
index 0b4c5d5093..9985cf2695 100644
--- a/tests/lean/phashmap_inst_coherence.lean
+++ b/tests/lean/phashmap_inst_coherence.lean
@@ -6,7 +6,7 @@ let m : PersistentHashMap Nat Nat := {};
 m.insert 1 1
 
 def natDiffHash : Hashable Nat :=
-⟨fun n => USize.ofNat $ n+10⟩
+⟨fun n => UInt64.ofNat $ n+10⟩
 
 -- The following example should fail since the `Hashable` instance used to create `m` is not `natDiffHash`
 #eval @PersistentHashMap.find? Nat Nat _ natDiffHash m 1