diff --git a/src/db/db/dbLibraryProxy.cc b/src/db/db/dbLibraryProxy.cc
index 92e0e27b4..4008a1253 100644
--- a/src/db/db/dbLibraryProxy.cc
+++ b/src/db/db/dbLibraryProxy.cc
@@ -42,14 +42,18 @@ LibraryProxy::LibraryProxy (db::cell_index_type ci, db::Layout &layout, lib_id_t
 
 LibraryProxy::~LibraryProxy ()
 {
-  if (layout ()) {
-    layout ()->unregister_lib_proxy (this);
-  }
-  if (db::LibraryManager::initialized ()) {
-    db::Library *lib = db::LibraryManager::instance ().lib (m_lib_id);
-    if (lib) {
-      lib->unregister_proxy (this, layout ());
+  try {
+    if (layout ()) {
+      layout ()->unregister_lib_proxy (this);
     }
+    if (db::LibraryManager::initialized ()) {
+      db::Library *lib = db::LibraryManager::instance ().lib (m_lib_id);
+      if (lib) {
+        lib->unregister_proxy (this, layout ());
+      }
+    }
+  } catch (...) {
+    //  ignore exceptions (may happen due to broken PCell instantiations)
   }
 }
 
diff --git a/src/db/db/gsiDeclDbCell.cc b/src/db/db/gsiDeclDbCell.cc
index 8d0bd4bcd..fce707adf 100644
--- a/src/db/db/gsiDeclDbCell.cc
+++ b/src/db/db/gsiDeclDbCell.cc
@@ -708,8 +708,19 @@ static gsi::layout_locking_iterator1<db::Shapes::shape_iterator> begin_overlappi
   return gsi::layout_locking_iterator1<db::Shapes::shape_iterator> (s->layout (), s->begin_overlapping (layer_index, db::CplxTrans (layout->dbu ()).inverted () * box, db::ShapeIterator::All));
 }
 
+static db::Instance insert_inst (db::Cell *c, const db::Cell::cell_inst_array_type &inst)
+{
+  if (c->layout () && ! c->layout ()->is_valid_cell_index (inst.object ().cell_index ())) {
+    throw tl::Exception (tl::to_string (tr ("Cell index is not valid")));
+  }
+  return c->insert (inst);
+}
+
 static db::Instance insert_inst_with_props (db::Cell *c, const db::Cell::cell_inst_array_type &inst, db::properties_id_type id)
 {
+  if (c->layout () && ! c->layout ()->is_valid_cell_index (inst.object ().cell_index ())) {
+    throw tl::Exception (tl::to_string (tr ("Cell index is not valid")));
+  }
   if (id) {
     return c->insert (db::CellInstArrayWithProperties (inst, id));
   } else {
@@ -2393,7 +2404,7 @@ Class<db::Cell> decl_Cell ("db", "Cell",
     "\n"
     "It has been added in version 0.16."
   ) +
-  gsi::method ("insert", (db::Instance (db::Cell::*)(const db::Cell::cell_inst_array_type &)) &db::Cell::insert, gsi::arg ("cell_inst_array"),
+  gsi::method_ext ("insert", &insert_inst, gsi::arg ("cell_inst_array"),
     "@brief Inserts a cell instance (array)\n"
     "@return An Instance object representing the new instance\n"
     "With version 0.16, this method returns an Instance object that represents the new instance.\n"
diff --git a/testdata/ruby/dbLayout.rb b/testdata/ruby/dbLayout.rb
index 9479f4f84..4b9f82480 100644
--- a/testdata/ruby/dbLayout.rb
+++ b/testdata/ruby/dbLayout.rb
@@ -2024,6 +2024,55 @@ class DBLayout_TestClass < TestBase
 
   end
 
+  def test_22
+
+    # invalid cell indexes
+   
+    l = RBA::Layout.new
+    l.insert_layer_at(0, RBA::LayerInfo.new(1, 0))
+    c0 = l.cell(l.add_cell("c0"))
+    c1 = l.cell(l.add_cell("c1"))
+    assert_equal(c0.cell_index, 0)
+    assert_equal(c1.cell_index, 1)
+
+    tt = RBA::Trans.new
+
+    error = 0
+    begin
+      c0.insert(RBA::CellInstArray.new(2, tt))
+    rescue
+      error = 1
+    end
+    assert_equal(error, 1)
+
+    error = 0
+    begin
+      c0.insert(RBA::CellInstArray.new(2, tt), 17)
+    rescue
+      error = 1
+    end
+    assert_equal(error, 1)
+
+    dtt = RBA::DTrans.new
+
+    error = 0
+    begin
+      c0.insert(RBA::DCellInstArray.new(2, dtt))
+    rescue
+      error = 1
+    end
+    assert_equal(error, 1)
+
+    error = 0
+    begin
+      c0.insert(RBA::DCellInstArray.new(2, dtt), 42)
+    rescue
+      error = 1
+    end
+    assert_equal(error, 1)
+
+  end
+
   # Iterating while flatten
   def test_issue200