diff --git a/specs/quint/specs/proofs-in-blocs/proofs.qnt b/specs/quint/specs/proofs-in-blocs/proofs.qnt
index 4088cacdb..5a287f0c9 100644
--- a/specs/quint/specs/proofs-in-blocs/proofs.qnt
+++ b/specs/quint/specs/proofs-in-blocs/proofs.qnt
@@ -24,7 +24,7 @@ type ForkID = int
 
 type L2Proof = {
     provenBlock: Height,
-    emptyBlocks: Set[int],
+    emptyBlocks: Set[Height],
 }
 
 type BlockProof =