diff --git a/plugins/3MFReader/WorkspaceDialog.py b/plugins/3MFReader/WorkspaceDialog.py
index 5e5eaf985e..349dec177b 100644
--- a/plugins/3MFReader/WorkspaceDialog.py
+++ b/plugins/3MFReader/WorkspaceDialog.py
@@ -285,14 +285,6 @@ class WorkspaceDialog(QObject):
         except:
             pass
 
-    @pyqtSlot(bool)
-    def _onVisibilityChanged(self, visible):
-        if not visible:
-            try:
-                self._lock.release()
-            except:
-                pass
-
     @pyqtSlot()
     def onOkButtonClicked(self):
         self._view.hide()