diff --git a/src/db/db/dbLayout.cc b/src/db/db/dbLayout.cc
index 52a9b5ff4..8210fbba5 100644
--- a/src/db/db/dbLayout.cc
+++ b/src/db/db/dbLayout.cc
@@ -1420,12 +1420,21 @@ Layout::topological_sort ()
 {
   m_top_cells = 0;
   m_top_down_list.clear ();
-  m_top_down_list.reserve (m_cells_size);
+
+  //  NOTE: we explicitly count the cells here and do not rely on "m_cell_size".
+  //  Reason is that this is somewhat safer, specifically directly after take() when
+  //  the cell list is already reduced, but the cell pointers are still containing the cell
+  //  (issue #905)
+  size_t ncells = 0;
+  for (const_iterator c = begin (); c != end (); ++c) {
+    ++ncells;
+  }
+  m_top_down_list.reserve (ncells);
 
   std::vector<size_t> num_parents (m_cell_ptrs.size (), 0);
 
   //  while there are cells to treat ..
-  while (m_top_down_list.size () != m_cells_size) {
+  while (m_top_down_list.size () != ncells) {
 
     size_t n_top_down_cells = m_top_down_list.size ();
 
diff --git a/src/db/unit_tests/dbLibrariesTests.cc b/src/db/unit_tests/dbLibrariesTests.cc
index c59c25e03..c60cd6c4f 100644
--- a/src/db/unit_tests/dbLibrariesTests.cc
+++ b/src/db/unit_tests/dbLibrariesTests.cc
@@ -700,3 +700,54 @@ TEST(4)
   }
 }
 
+namespace {
+
+class PCell1Declaration :
+  public db::PCellDeclaration
+{
+  void produce (const db::Layout & /*layout*/, const std::vector<unsigned int> & /*layer_ids*/, const db::pcell_parameters_type & /*parameters*/, db::Cell & /*cell*/) const
+  {
+    // ...
+  }
+};
+
+class PCell2Declaration :
+  public db::PCellDeclaration
+{
+  void produce (const db::Layout & /*layout*/, const std::vector<unsigned int> & /*layer_ids*/, const db::pcell_parameters_type & /*parameters*/, db::Cell &cell) const
+  {
+    //  NOTE: this is the self-reference: we use the library which defines the PCell and create a proxy to itself
+    std::pair<bool, db::lib_id_type> l = db::LibraryManager::instance ().lib_by_name ("__PCellLibrary");
+    tl_assert (l.first);
+    db::Library *lib = db::LibraryManager::instance ().lib (l.second);
+    std::pair<bool, db::pcell_id_type> pcell_id = lib->layout ().pcell_by_name ("PCell1");
+    tl_assert (pcell_id.first);
+    db::cell_index_type pcell_var = lib->layout ().get_pcell_variant_dict (pcell_id.second, std::map<std::string, tl::Variant> ());
+
+    db::cell_index_type lib_cell = cell.layout ()->get_lib_proxy (lib, pcell_var);
+    cell.insert (db::CellInstArray (lib_cell, db::Trans ()));
+  }
+};
+
+}
+
+//  self-referencing libraries
+TEST(5_issue905)
+{
+  std::unique_ptr<db::Library> lib;
+  lib.reset (new db::Library ());
+  lib->set_name ("__PCellLibrary");
+  lib->layout ().register_pcell ("PCell1", new PCell1Declaration ());
+  lib->layout ().register_pcell ("PCell2", new PCell2Declaration ());
+  db::LibraryManager::instance ().register_lib (lib.get ());
+
+  db::Layout ly;
+  std::pair<bool, db::pcell_id_type> pc = lib->layout ().pcell_by_name ("PCell2");
+  tl_assert (pc.first);
+
+  db::cell_index_type lib_cell = lib->layout ().get_pcell_variant_dict (pc.second, std::map<std::string, tl::Variant> ());
+  ly.get_lib_proxy (lib.get (), lib_cell);
+
+  db::LibraryManager::instance ().delete_lib (lib.release ());
+  EXPECT (true);
+}