diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1c536981..c19ff2c4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ CHANGELOG for FlatCAM beta
 2.09.2021
 
 - in Geometry Editor, deleting a shape from the Table context menu will update now the plot
+- when a Plugin is no longer used disconnect a certain signal that control the selection in the App Object Target combobox since it is not needed and it takes cpu cycles
 
 1.09.2021
 
diff --git a/app_Main.py b/app_Main.py
index 75fbac7c..43f65da0 100644
--- a/app_Main.py
+++ b/app_Main.py
@@ -6704,6 +6704,14 @@ class App(QtCore.QObject):
         # except Exception as err:
         #     print(str(err))
 
+        try:
+            # this signal is used by the Plugins to change the selection on App objects combo boxes when the
+            # selection happen in Project Tab (collection view)
+            # when the plugin is closed then it's not needed
+            self.proj_selection_changed.disconnect()
+        except (TypeError, AttributeError):
+            pass
+
         try:
             # clear the possible drawn probing shapes for Levelling Tool
             self.levelling_tool.probing_shapes.clear(update=True)