diff --git a/fs/bcachefs/fs-io.c b/fs/bcachefs/fs-io.c
index d98b654c92b1..e25dbbf46107 100644
--- a/fs/bcachefs/fs-io.c
+++ b/fs/bcachefs/fs-io.c
@@ -2682,6 +2682,8 @@ static int __bch2_truncate_page(struct bch_inode_info *inode,
 			goto unlock;
 	}
 
+	BUG_ON(!s->uptodate);
+
 	if (index != start >> PAGE_SHIFT)
 		start_offset = 0;
 	if (index != end >> PAGE_SHIFT)