diff --git a/src/gui_builder.cc b/src/gui_builder.cc
index 12304b3..f9bcb94 100644
--- a/src/gui_builder.cc
+++ b/src/gui_builder.cc
@@ -225,8 +225,15 @@ GuiBuilder::on_file_saveas_activate()
     int result = dialog.run();
     if(result==Gtk::RESPONSE_OK)
     {
-      serializer.save_snapshot(dialog.get_filename(), history);
       _filename = dialog.get_filename();
+
+      // Append standard extension if none (or a different one) is provided
+      std::string ext = std::string(".") + serializer.get_filename_extension();
+      if(_filename.size() < ext.size() || _filename.substr(_filename.size() - ext.size()) != ext)
+        _filename += ext;
+
+      serializer.save_snapshot(_filename, history);
+
       msg = "File: " + _filename + " saved.";
     } // end - if(result==Gtk::RESPONSE_OK)