diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 9761a5befef0..f3cc4ab20ba0 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -1283,13 +1283,18 @@ __xfs_get_blocks(
 	bh_result->b_bdev = iomap.iomap_target->bt_bdev;
 
 	/*
-	 * If we previously allocated a block out beyond eof and we are
-	 * now coming back to use it then we will need to flag it as new
-	 * even if it has a disk address.
+	 * If we previously allocated a block out beyond eof and we are now
+	 * coming back to use it then we will need to flag it as new even if it
+	 * has a disk address.
+	 *
+	 * With sub-block writes into unwritten extents we also need to mark
+	 * the buffer as new so that the unwritten parts of the buffer gets
+	 * correctly zeroed.
 	 */
 	if (create &&
 	    ((!buffer_mapped(bh_result) && !buffer_uptodate(bh_result)) ||
-	     (offset >= i_size_read(inode)) || (iomap.iomap_flags & IOMAP_NEW)))
+	     (offset >= i_size_read(inode)) ||
+	     (iomap.iomap_flags & (IOMAP_NEW|IOMAP_UNWRITTEN))))
 		set_buffer_new(bh_result);
 
 	if (iomap.iomap_flags & IOMAP_DELAY) {