diff --git a/src/hb-graphite2.cc b/src/hb-graphite2.cc
index 807c33087..26619e1ce 100644
--- a/src/hb-graphite2.cc
+++ b/src/hb-graphite2.cc
@@ -269,6 +269,7 @@ _hb_graphite2_shape (hb_shape_plan_t    *shape_plan,
     gr_seg_destroy (seg);
     return false;
   }
+  buffer->ensure (glyph_count);
 
   scratch = buffer->get_scratch_buffer (&scratch_size);
   while ((DIV_CEIL (sizeof (hb_graphite2_cluster_t) * buffer->len, sizeof (*scratch)) +