diff --git a/qtgui/instrument.py b/qtgui/instrument.py
index 920b7b6..63e0b61 100644
--- a/qtgui/instrument.py
+++ b/qtgui/instrument.py
@@ -113,7 +113,8 @@ class InstrumentTreeController(object):
 
 
     def itemExpandedOrCollapsed(self, libraryItem:QtWidgets.QTreeWidgetItem):
-        api.session.guiSharedDataToSave["libraryIsExpanded"][libraryItem.id] = libraryItem.isExpanded()
+        if type(libraryItem) is GuiLibrary : #just in case
+            api.session.guiSharedDataToSave["libraryIsExpanded"][libraryItem.id] = libraryItem.isExpanded()
 
     def itemSelectionChanged(self):
         """Only one instrument can be selected at the same time.