diff --git a/reftable/pq.h b/reftable/pq.h
index e85bac9b52..9e25a43a36 100644
--- a/reftable/pq.h
+++ b/reftable/pq.h
@@ -12,7 +12,7 @@ https://developers.google.com/open-source/licenses/bsd
 #include "record.h"
 
 struct pq_entry {
-	int index;
+	size_t index;
 	struct reftable_record rec;
 };