Index: btrfs-progs-v0.20-rc1-335-gf00dd83/mkfs.c
===================================================================
--- btrfs-progs-v0.20-rc1-335-gf00dd83.orig/mkfs.c
+++ btrfs-progs-v0.20-rc1-335-gf00dd83/mkfs.c
@@ -1520,6 +1520,8 @@ raid_groups:
 
 	super = root->fs_info->super_copy;
 	flags = btrfs_super_incompat_flags(super);
+	printf("Turning on extended refs (higher hardlink limit)\n");
+	flags |= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF;
 
 	if (mixed)
 		flags |= BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS;