diff --git a/refs.c b/refs.c
index ad6d774717..ef04f403a6 100644
--- a/refs.c
+++ b/refs.c
@@ -1331,7 +1331,7 @@ static int ref_transaction_update_reflog(struct ref_transaction *transaction,
 					 const char *committer_info,
 					 unsigned int flags,
 					 const char *msg,
-					 unsigned int index,
+					 uint64_t index,
 					 struct strbuf *err)
 {
 	struct ref_update *update;
@@ -2813,7 +2813,7 @@ done:
 }
 
 struct reflog_migration_data {
-	unsigned int index;
+	uint64_t index;
 	const char *refname;
 	struct ref_store *old_refs;
 	struct ref_transaction *transaction;
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index aaab711bb9..8894b43d1d 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -120,7 +120,7 @@ struct ref_update {
 	 * when migrating reflogs and we want to ensure we carry over the
 	 * same order.
 	 */
-	unsigned int index;
+	uint64_t index;
 
 	/*
 	 * If this ref_update was split off of a symref update via
@@ -203,7 +203,7 @@ struct ref_transaction {
 	enum ref_transaction_state state;
 	void *backend_data;
 	unsigned int flags;
-	unsigned int max_index;
+	uint64_t max_index;
 };
 
 /*
diff --git a/refs/reftable-backend.c b/refs/reftable-backend.c
index 289496058e..6814c87bc6 100644
--- a/refs/reftable-backend.c
+++ b/refs/reftable-backend.c
@@ -942,7 +942,7 @@ struct write_transaction_table_arg {
 	size_t updates_nr;
 	size_t updates_alloc;
 	size_t updates_expected;
-	unsigned int max_index;
+	uint64_t max_index;
 };
 
 struct reftable_transaction_data {