diff --git a/src/hb-aat-layout-trak-table.hh b/src/hb-aat-layout-trak-table.hh
index 0617e23..f5dc558 100644
--- a/src/hb-aat-layout-trak-table.hh
+++ b/src/hb-aat-layout-trak-table.hh
@@ -172,7 +172,7 @@
       hb_position_t advance_to_add = c->font->em_scalef_x (tracking / 2);
       foreach_grapheme (buffer, start, end)
       {
-	/* TODO This is wrong. */
+	buffer->pos[start].x_offset += advance_to_add;
 	buffer->pos[start].x_advance += advance_to_add;
 	buffer->pos[end].x_advance += advance_to_add;
       }
@@ -184,7 +184,7 @@
       hb_position_t advance_to_add = c->font->em_scalef_y (tracking / 2);
       foreach_grapheme (buffer, start, end)
       {
-	/* TODO This is wrong. */
+	buffer->pos[start].y_offset += advance_to_add;
 	buffer->pos[start].y_advance += advance_to_add;
 	buffer->pos[end].y_advance += advance_to_add;
       }