diff --git a/src/hb-aat-layout-kerx-table.hh b/src/hb-aat-layout-kerx-table.hh
index 019efd57e..a54e29781 100644
--- a/src/hb-aat-layout-kerx-table.hh
+++ b/src/hb-aat-layout-kerx-table.hh
@@ -343,6 +343,7 @@ struct KerxSubTableFormat4
 
       if (mark_set && entry->data.ankrActionIndex != 0xFFFF)
       {
+	hb_glyph_position_t &o = buffer->cur_pos();
 	switch (action_type)
 	{
 	  case 0: /* Control Point Actions.*/
@@ -373,12 +374,9 @@ struct KerxSubTableFormat4
 								currAnchorPoint,
 								c->face->get_num_glyphs (),
 								c->ankr_end);
-	    hb_glyph_position_t &o = buffer->cur_pos();
+
 	    o.x_offset = c->font->em_scale_x (markAnchor.xCoordinate) - c->font->em_scale_x (currAnchor.xCoordinate);
 	    o.y_offset = c->font->em_scale_y (markAnchor.yCoordinate) - c->font->em_scale_y (currAnchor.yCoordinate);
-	    o.attach_type() = ATTACH_TYPE_MARK;
-	    o.attach_chain() = (int) mark - (int) buffer->idx;
-	    buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
 	  }
 	  break;
 
@@ -387,14 +385,19 @@ struct KerxSubTableFormat4
 	    const FWORD *data = (const FWORD *) &ankrData[entry->data.ankrActionIndex];
 	    if (!c->sanitizer.check_array (data, 4))
 	      return false;
-	    HB_UNUSED int markX = *data++;
-	    HB_UNUSED int markY = *data++;
-	    HB_UNUSED int currX = *data++;
-	    HB_UNUSED int currY = *data++;
-	    /* TODO */
+	    int markX = *data++;
+	    int markY = *data++;
+	    int currX = *data++;
+	    int currY = *data++;
+
+	    o.x_offset = c->font->em_scale_x (markX) - c->font->em_scale_x (currX);
+	    o.y_offset = c->font->em_scale_y (markY) - c->font->em_scale_y (currY);
 	  }
 	  break;
 	}
+	o.attach_type() = ATTACH_TYPE_MARK;
+	o.attach_chain() = (int) mark - (int) buffer->idx;
+	buffer->scratch_flags |= HB_BUFFER_SCRATCH_FLAG_HAS_GPOS_ATTACHMENT;
       }
 
       if (flags & Mark)