diff --git a/src/backend/utils/adt/amutils.c b/src/backend/utils/adt/amutils.c
index 48852bf79e2..1ace63aa87d 100644
--- a/src/backend/utils/adt/amutils.c
+++ b/src/backend/utils/adt/amutils.c
@@ -451,7 +451,7 @@ Datum
 pg_indexam_progress_phasename(PG_FUNCTION_ARGS)
 {
 	Oid			amoid = PG_GETARG_OID(0);
-	int32		phasenum = PG_GETARG_INT32(1);
+	int64		phasenum = PG_GETARG_INT64(1);
 	IndexAmRoutine *routine;
 	char	   *name;