diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 478cf446827f..35bd3a62451b 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3893,6 +3893,13 @@ static int raid10_run(struct mddev *mddev)
 			    disk->rdev->saved_raid_disk < 0)
 				conf->fullsync = 1;
 		}
+
+		if (disk->replacement &&
+		    !test_bit(In_sync, &disk->replacement->flags) &&
+		    disk->replacement->saved_raid_disk < 0) {
+			conf->fullsync = 1;
+		}
+
 		disk->recovery_disabled = mddev->recovery_disabled - 1;
 	}