diff --git a/triqs/gfs/meshes/matsubara_freq.hpp b/triqs/gfs/meshes/matsubara_freq.hpp
index b8803b3d..b7d0f031 100644
--- a/triqs/gfs/meshes/matsubara_freq.hpp
+++ b/triqs/gfs/meshes/matsubara_freq.hpp
@@ -38,7 +38,8 @@ namespace gfs {
      : _dom(std::move(dom)), n_max(n_pts), _positive_only(positive_only) {}
 
   domain_t const &domain() const { return _dom; }
-  size_t size() const { return (_positive_only ? n_max : 2 * n_max + 1); }
+  int index_start() const { return -(_positive_only ? 0 : n_max + (_dom.statistic == Fermion)); }
+  size_t size() const { return (_positive_only ? n_max : 2 * n_max + (_dom.statistic == Boson ? 1 : 2)); }
 
   /// Conversions point <-> index <-> linear_index
   domain_pt_t index_to_point(index_t ind) const {
@@ -46,21 +47,21 @@ namespace gfs {
   }
 
   public:
-  size_t index_to_linear(index_t ind) const { return ind; }
+  int index_to_linear(index_t ind) const { return ind + index_start(); }
 
-  /// The wrapper for the mesh point
+  /// The mesh point
   struct mesh_point_t : tag::mesh_point, matsubara_freq {
-   index_t n_max;
+   index_t index_start, index_stop;
    mesh_point_t() = default;
    mesh_point_t(matsubara_freq_mesh const &mesh, index_t const &index_)
-      : matsubara_freq(index_, mesh.domain().beta, mesh.domain().statistic), n_max(mesh.size()) {}
-   mesh_point_t(index_t const &index_, double beta_, statistic_enum stat_, index_t n_max_)
-      : matsubara_freq(index_, beta_, stat_), n_max(n_max_) {}
+      : matsubara_freq(index_, mesh.domain().beta, mesh.domain().statistic),
+        index_start(mesh.index_start()),
+        index_stop(mesh.index_start() + mesh.size() - 1) {}
    void advance() { ++n; }
    size_t linear_index() const { return n; }
    size_t index() const { return n; }
-   bool at_end() const { return (n == n_max); }
-   void reset() { n = 0; }
+   bool at_end() const { return (n == index_stop); }
+   void reset() { n = index_start; }
   };
 
   /// Accessing a point of the mesh
@@ -84,12 +85,16 @@ namespace gfs {
    h5::group gr = fg.create_group(subgroup_name);
    h5_write(gr, "domain", m.domain());
    h5_write(gr, "size", m.size());
-   // h5_write(gr, "start_at_0", m._positive_only);
-   // kept for backward compatibility
-   auto beta = m.domain().beta;
-   h5_write(gr, "min", Fermion ? M_PI / beta : 0);
-   h5_write(gr, "max", ((Fermion ? 1 : 0) + 2 * m.size()) * M_PI / beta);
-   h5_write(gr, "kind", 2);
+   if (m._positive_only) {
+    // h5_write(gr, "start_at_0", m._positive_only);
+    // kept for backward compatibility
+    auto beta = m.domain().beta;
+    h5_write(gr, "min", Fermion ? M_PI / beta : 0);
+    h5_write(gr, "max", ((Fermion ? 1 : 0) + 2 * m.size()) * M_PI / beta);
+    h5_write(gr, "kind", 2);
+   } else { // A strange way : to preserve backward compatibility for old archive.
+    h5_write(gr, "start_at_0", m._positive_only);
+   }
   }
 
   /// Read from HDF5
@@ -100,7 +105,7 @@ namespace gfs {
    bool s = true;
    h5_read(gr, "domain", dom);
    h5_read(gr, "size", L);
-   // h5_read(gr, "start_at_0", s);
+   if (gr.has_key("start_at_0")) h5_read(gr, "start_at_0", s);
    m = matsubara_freq_mesh{std::move(dom), L, s};
   }