diff --git a/src/hb-ot-shape-fallback.cc b/src/hb-ot-shape-fallback.cc
index 53274b502..748372d01 100644
--- a/src/hb-ot-shape-fallback.cc
+++ b/src/hb-ot-shape-fallback.cc
@@ -418,13 +418,12 @@ _hb_ot_shape_fallback_position (const hb_ot_shape_plan_t *plan,
   _hb_buffer_assert_gsubgpos_vars (buffer);
 
   unsigned int start = 0;
-  unsigned int last_cluster = buffer->info[0].cluster;
   unsigned int count = buffer->len;
+  hb_glyph_info_t *info = buffer->info;
   for (unsigned int i = 1; i < count; i++)
-    if (buffer->info[i].cluster != last_cluster) {
+    if (likely (!HB_UNICODE_GENERAL_CATEGORY_IS_MARK (_hb_glyph_info_get_general_category (&info[i])))) {
       position_cluster (plan, font, buffer, start, i);
       start = i;
-      last_cluster = buffer->info[i].cluster;
     }
   position_cluster (plan, font, buffer, start, count);
 }