diff --git a/pcbnew/python/scripting/pcbnew_scripting_helpers.cpp b/pcbnew/python/scripting/pcbnew_scripting_helpers.cpp
index 0cfd105820..f18cc58cda 100644
--- a/pcbnew/python/scripting/pcbnew_scripting_helpers.cpp
+++ b/pcbnew/python/scripting/pcbnew_scripting_helpers.cpp
@@ -47,6 +47,8 @@
 #include <macros.h>
 #include <pcbnew_scripting_helpers.h>
 #include <project.h>
+#include <project/net_settings.h>
+#include <project/project_file.h>
 #include <settings/settings_manager.h>
 #include <specctra.h>
 #include <project/project_local_settings.h>
@@ -158,6 +160,9 @@ BOARD* LoadBoard( wxString& aFileName, IO_MGR::PCB_FILE_T aFormat )
     {
         brd->SetProject( project );
 
+        if( brd->m_LegacyDesignSettingsLoaded )
+            project->GetProjectFile().NetSettings().RebuildNetClassAssignments();
+
         // Move legacy view settings to local project settings
         if( !brd->m_LegacyVisibleLayers.test( Rescue ) )
             project->GetLocalSettings().m_VisibleLayers = brd->m_LegacyVisibleLayers;