diff --git a/src/db/db/dbCommonReader.cc b/src/db/db/dbCommonReader.cc
index ab72d234a..1e6d49e7d 100644
--- a/src/db/db/dbCommonReader.cc
+++ b/src/db/db/dbCommonReader.cc
@@ -286,6 +286,8 @@ CommonReader::read (db::Layout &layout, const db::LoadLayoutOptions &options)
 {
   init (options);
 
+  tl_assert (!layout.under_construction ());
+
   m_common_options.layer_map.prepare (layout);
 
   layout.start_changes ();
@@ -298,6 +300,11 @@ CommonReader::read (db::Layout &layout, const db::LoadLayoutOptions &options)
     throw;
   }
 
+  //  A cleanup may be necessary because of the following scenario: if library proxies contain subcells
+  //  which are proxies itself, the proxy update may make them orphans (the proxies are regenerated).
+  //  The cleanup will removed these.
+  layout.cleanup ();
+
   return m_layer_map_out;
 }