diff --git a/src/hb-private.hh b/src/hb-private.hh
index 5deaa9d9a0d46fea673b0755816e412b5562f169..3c0049283a4c0c1a34a88201dfde85d2e20af237 100644
--- a/src/hb-private.hh
+++ b/src/hb-private.hh
@@ -1116,7 +1116,7 @@ struct hb_vector_size_t
   }
 
   private:
-  static_assert (byte_size / sizeof (elt_t) * sizeof (elt_t) == byte_size);
+  static_assert (byte_size / sizeof (elt_t) * sizeof (elt_t) == byte_size, "");
   elt_t v[byte_size / sizeof (elt_t)];
 };