diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c
index 20dad22c4b7..58e3867246f 100644
--- a/src/backend/commands/repack.c
+++ b/src/backend/commands/repack.c
@@ -2710,11 +2710,7 @@ restore_tuple(BufFile *file, Relation relation, TupleTableSlot *slot)
 		{
 			CompactAttribute *attr = TupleDescCompactAttr(desc, i);
 			varlena    *varlen;
-			union
-			{
-				alignas(int32) varlena hdr;
-				char		data[sizeof(void *)];
-			}			chunk_header;
+			uint64		chunk_header;
 			void	   *value;
 			Size		varlensz;