diff --git a/triqs/utility/tuple_tools.hpp b/triqs/utility/tuple_tools.hpp
index 538cbd07..bb6a61db 100644
--- a/triqs/utility/tuple_tools.hpp
+++ b/triqs/utility/tuple_tools.hpp
@@ -109,19 +109,19 @@ namespace triqs { namespace tuple {
   * t1, t2 two tuples of the same size
   * Returns : [f(i,j) for i,j in zip(t1,t2)]
   */
- template<int pos, typename T1, typename T2> struct apply_on_zip_impl {
-  template<typename F, typename ... Args>
-   auto operator()(F && f, T1 const & t1, T2 const & t2, Args && ... args)
-   DECL_AND_RETURN( apply_on_zip_impl<pos-1,T1,T2>()(std::forward<F>(f),t1, t2, f(std::get<pos>(t1),std::get<pos>(t2)), std::forward<Args>(args)...));
+ template<int pos> struct apply_on_zip_impl {
+  template<typename F, typename T1, typename T2, typename ... Args>
+   auto operator()(F && f, T1 && t1, T2 && t2,  Args && ... args)
+   DECL_AND_RETURN( apply_on_zip_impl<pos-1>()(std::forward<F>(f),std::forward<T1>(t1), std::forward<T2>(t2),  f(std::get<pos>(t1),std::get<pos>(t2)), std::forward<Args>(args)...));
  };
 
- template<typename T1, typename T2> struct apply_on_zip_impl<-1,T1,T2> {
-  template<typename F, typename ... Args>
-   auto operator()(F && f, T1 const & t1, T2 const & t2, Args && ... args) DECL_AND_RETURN( std::make_tuple(std::forward<Args>(args)...));
+ template<> struct apply_on_zip_impl<-1> {
+  template<typename F, typename T1, typename T2, typename ... Args>
+   auto operator()(F && f, T1 && t1, T2 && t2, Args && ... args) DECL_AND_RETURN( std::make_tuple(std::forward<Args>(args)...));
  };
 
  template<typename F, typename T1, typename T2>
-  auto apply_on_zip (F && f,T1 const & t1, T2 const & t2) DECL_AND_RETURN( apply_on_zip_impl<std::tuple_size<T1>::value-1,T1,T2>()(std::forward<F>(f),t1,t2));
+  auto apply_on_zip (F && f,T1 && t1, T2 && t2) DECL_AND_RETURN( apply_on_zip_impl<std::tuple_size<typename std::remove_reference<T1>::type>::value-1>()(std::forward<F>(f),std::forward<T1>(t1),std::forward<T2>(t2)));
 
  /**
   * apply_on_tuple(f, t1,t2,t3)
@@ -129,19 +129,20 @@ namespace triqs { namespace tuple {
   * t1, t2 two tuples of the same size
   * Returns : [f(i,j) for i,j in zip(t1,t2)]
   */
- template<int pos, typename T1, typename T2, typename T3> struct apply_on_zip3_impl {
-  template<typename F, typename ... Args>
-   auto operator()(F && f, T1 const & t1, T2 const & t2, T3 const & t3, Args && ... args)
-   DECL_AND_RETURN( apply_on_zip3_impl<pos-1,T1,T2,T3>()(std::forward<F>(f),t1, t2, t3, f(std::get<pos>(t1),std::get<pos>(t2),std::get<pos>(t3)), std::forward<Args>(args)...));
+ template<int pos> struct apply_on_zip3_impl {
+  template<typename F, typename T1, typename T2, typename T3, typename ... Args>
+   auto operator()(F && f, T1 && t1, T2 && t2, T3 && t3, Args && ... args)
+   DECL_AND_RETURN( apply_on_zip3_impl<pos-1>()(std::forward<F>(f),std::forward<T1>(t1), std::forward<T2>(t2), std::forward<T3>(t3), 
+      f(std::get<pos>(t1),std::get<pos>(t2),std::get<pos>(t3)), std::forward<Args>(args)...));
  };
 
- template<typename T1, typename T2, typename T3> struct apply_on_zip3_impl<-1,T1,T2,T3> {
-  template<typename F, typename ... Args>
-   auto operator()(F && f, T1 const & t1, T2 const & t2,  T3 const & t3, Args && ... args) DECL_AND_RETURN( std::make_tuple(std::forward<Args>(args)...));
+ template<> struct apply_on_zip3_impl<-1> {
+  template<typename F, typename T1, typename T2, typename T3,typename ... Args>
+   auto operator()(F && f, T1 && t1, T2 && t2,  T3 && t3, Args && ... args) DECL_AND_RETURN( std::make_tuple(std::forward<Args>(args)...));
  };
 
  template<typename F, typename T1, typename T2, typename T3>
-  auto apply_on_zip3 (F && f,T1 const & t1, T2 const & t2, T3 const & t3) DECL_AND_RETURN( apply_on_zip3_impl<std::tuple_size<T1>::value-1,T1,T2,T3>()(std::forward<F>(f),t1,t2,t3));
+  auto apply_on_zip3 (F && f,T1 && t1, T2 && t2, T3 && t3) DECL_AND_RETURN( apply_on_zip3_impl<std::tuple_size<typename std::remove_reference<T1>::type>::value-1>()(std::forward<F>(f),std::forward<T1>(t1),std::forward<T2>(t2),std::forward<T3>(t3)));
 
  /**
   * fold(f, t1, init)