diff --git a/plugins/core-plugin.cc b/plugins/core-plugin.cc
index 0881d85..55580bc 100644
--- a/plugins/core-plugin.cc
+++ b/plugins/core-plugin.cc
@@ -119,6 +119,9 @@ namespace clap {
          ClapOStream os(stream);
          yas::binary_oarchive ar(os);
          ar & _parameters;
+
+         std::vector<uint8_t> extra = stateSaveExtra();
+         ar & extra;
       } catch (...) {
          return false;
       }
@@ -138,6 +141,11 @@ namespace clap {
 #endif
          yas::binary_iarchive ar(is);
          ar & _parameters;
+
+         std::vector<uint8_t> extra;
+         ar & extra;
+         if (!stateLoadExtra(extra))
+            return false;
       } catch (...) {
          return false;
       }
diff --git a/plugins/core-plugin.hh b/plugins/core-plugin.hh
index 7752183..59648f9 100644
--- a/plugins/core-plugin.hh
+++ b/plugins/core-plugin.hh
@@ -3,6 +3,9 @@
 #include <memory>
 #include <optional>
 
+#include <yas/binary_iarchive.hpp>
+#include <yas/binary_oarchive.hpp>
+
 #include <clap/helpers/param-queue.hh>
 #include <clap/helpers/plugin.hh>
 #include <clap/helpers/reducing-param-queue.hxx>
@@ -148,6 +151,9 @@ namespace clap {
       bool stateSave(const clap_ostream *stream) noexcept override;
       bool stateLoad(const clap_istream *stream) noexcept override;
 
+      virtual std::vector<uint8_t> stateSaveExtra() noexcept { return {}; }
+      virtual bool stateLoadExtra(const std::vector<uint8_t>& data) noexcept { return true; }
+
 #ifndef CLAP_PLUGINS_HEADLESS
       //-----------------//
       // clap_plugin_gui //
diff --git a/plugins/plugs/undo-test/undo-test.cc b/plugins/plugs/undo-test/undo-test.cc
index 1f6802d..04e8841 100644
--- a/plugins/plugs/undo-test/undo-test.cc
+++ b/plugins/plugs/undo-test/undo-test.cc
@@ -132,4 +132,16 @@ namespace clap {
          super::onGuiInvoke(method, args);
    }
 #endif
+
+   std::vector<uint8_t> UndoTest::stateSaveExtra() noexcept {
+      return std::vector<uint8_t>((const uint8_t *)&_state, (const uint8_t *)(&_state + 1));
+   }
+
+   bool UndoTest::stateLoadExtra(const std::vector<uint8_t> &data) noexcept {
+      if (data.size() != sizeof(_state))
+         return false;
+      _state = *(const uint32_t *)data.data();
+      return true;
+   }
+
 } // namespace clap
diff --git a/plugins/plugs/undo-test/undo-test.hh b/plugins/plugs/undo-test/undo-test.hh
index d3f923a..914ce50 100644
--- a/plugins/plugs/undo-test/undo-test.hh
+++ b/plugins/plugs/undo-test/undo-test.hh
@@ -17,6 +17,9 @@ namespace clap {
 
       bool init() noexcept override;
 
+      std::vector<uint8_t> stateSaveExtra() noexcept override;
+      bool stateLoadExtra(const std::vector<uint8_t> &data) noexcept override;
+
       bool implementsUndo() const noexcept override;
       void undoGetDeltaProperties(clap_undo_delta_properties_t *properties) noexcept override;
       bool undoCanUseDeltaFormatVersion(clap_id format_version) noexcept override;