diff --git a/triqs/utility/index_generator.hpp b/triqs/utility/index_generator.hpp
index decf97cf..fa16966b 100644
--- a/triqs/utility/index_generator.hpp
+++ b/triqs/utility/index_generator.hpp
@@ -45,7 +45,7 @@ namespace utility {
    // i[0]=0;
    _at_end = true;
   }
-  AUTO_DECL index() const { return i; }
+  AUTO_DECL index() const RETURN(i);
   long linear_index() const { return i_flat;}
   bool at_end() const { return _at_end; }
   void reset() {