diff --git a/pyproject.toml b/pyproject.toml
index 1eeaca1..c873803 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,9 @@ build-backend = "flit_core.buildapi"
 [project]
 name = "natlinkcore"
 authors = [{name = "Quintijn Hoogenboom (maintainer)", email = "q.hoogenboom@antenna.nl"}]
-version="5.4.2"
+
+version="5.4.3"
+
 dynamic = [ "description"]
 requires-python = ">=3.10"
 readme = "readme.md"
diff --git a/src/natlinkcore/loader.py b/src/natlinkcore/loader.py
index 2b0f4ec..5be9e36 100644
--- a/src/natlinkcore/loader.py
+++ b/src/natlinkcore/loader.py
@@ -561,11 +561,18 @@ def start(self) -> None:
             self.trigger_load()
         natlink.setBeginCallback(self.on_begin_callback)
         natlink.setChangeCallback(self.on_change_callback)
-        natlink.setMessageWindow(self.on_message_window_callback)
+        try:
+            natlink.setMessageWindow(self.on_message_window_callback)
+        except AttributeError:
+            pass
+
 
     def finish(self) -> None:
         # reverse changes made by start()
-        natlink.setMessageWindow(None)
+        try:
+            natlink.setMessageWindow(None)
+        except AttributeError:
+            pass
         natlink.setChangeCallback(None)
         natlink.setBeginCallback(None)
         self.unload_all_loaded_modules()