diff --git a/src/hb-ot-cff-common.hh b/src/hb-ot-cff-common.hh
index 89f23b4b2..17641aa68 100644
--- a/src/hb-ot-cff-common.hh
+++ b/src/hb-ot-cff-common.hh
@@ -57,14 +57,11 @@ struct str_buff_vec_t : hb_vector_t<str_buff_t>
 {
   unsigned int total_size () const
   {
-    unsigned int size = 0;
-    for (const auto& v : *this )
-      size += v.length;
-    return size;
+    return + this->iter ()
+	   | hb_map (&str_buff_t::length)
+	   | hb_reduce (hb_add, 0)
+	   ;
   }
-
-  private:
-  typedef hb_vector_t<str_buff_t> SUPER;
 };
 
 /* CFF INDEX */