diff --git a/src/hb-buffer.cc b/src/hb-buffer.cc
index 2a9849756..8ccfea5f3 100644
--- a/src/hb-buffer.cc
+++ b/src/hb-buffer.cc
@@ -468,6 +468,11 @@ hb_buffer_t::merge_out_clusters (unsigned int start,
   while (end < out_len && out_info[end - 1].cluster == out_info[end].cluster)
     end++;
 
+  /* If we hit the end of out-buffer, continue in buffer. */
+  if (end == out_len)
+    for (unsigned i = idx; i < len && info[i].cluster == out_info[end - 1].cluster; i++)
+      info[i].cluster = cluster;
+
   for (unsigned int i = start; i < end; i++)
     out_info[i].cluster = cluster;
 }
diff --git a/src/hb-ot-shape-complex-misc.cc b/src/hb-ot-shape-complex-misc.cc
index 748d4b331..52fbd6d31 100644
--- a/src/hb-ot-shape-complex-misc.cc
+++ b/src/hb-ot-shape-complex-misc.cc
@@ -176,15 +176,6 @@ _hb_ot_shape_complex_setup_masks_thai (hb_ot_map_t *map HB_UNUSED,
 	     sizeof (buffer->out_info[0]) * (end - start - 2));
     buffer->out_info[start] = t;
 
-    /* XXX Make this easier! */
-    /* Make cluster */
-    for (; buffer->idx < count;)
-      if (buffer->cur().cluster == buffer->prev().cluster)
-        buffer->next_glyph ();
-      else
-        break;
-    end = buffer->out_len;
-
     buffer->merge_out_clusters (start, end);
   }
   buffer->swap_buffers ();