diff --git a/src/hashset.hpp b/src/hashset.hpp
index a77dbc93..ce962a1f 100644
--- a/src/hashset.hpp
+++ b/src/hashset.hpp
@@ -107,7 +107,7 @@ public:
   int
   size(void)
   {
-    return str_set_size(&_str_set);
+    return u64_set_size(&_str_set);
     return kh_size(_set);
   }