diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c72bd6190a..ce4eef950b 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2758,7 +2758,7 @@ static struct config_int ConfigureNamesInt[] =
 			GUC_UNIT_BLOCKS,
 		},
 		&min_parallel_relation_size,
-		1024, 0, INT_MAX / 3,
+		(8 * 1024 * 1024) / BLCKSZ, 0, INT_MAX / 3,
 		NULL, NULL, NULL
 	},