diff --git a/src/hb-ot-var-common.hh b/src/hb-ot-var-common.hh
index c09ea49..5af8085 100644
--- a/src/hb-ot-var-common.hh
+++ b/src/hb-ot-var-common.hh
@@ -982,7 +982,7 @@
           return false;
 
 	hb_hashmap_t<hb_tag_t, Triple> axis_tuples;
-	axis_tuples.allocate_from_pool (pool, iterator.get_axis_count ());
+	axis_tuples.allocate_from_pool (pool, 3);
 
         if (!iterator.current_tuple->unpack_axis_tuples (iterator.get_axis_count (), shared_tuples, axes_old_index_tag_map, axis_tuples)
             || axis_tuples.is_empty ())