--- a/PluginManager/PluginInstallDialog.py	Wed Aug 19 11:00:48 2015 +0200
+++ b/PluginManager/PluginInstallDialog.py	Fri Aug 21 14:16:37 2015 +0200
@@ -211,6 +211,9 @@
         elif button == self.__finishButton:
             self.__finishButton.setEnabled(False)
             self.__installPlugins()
+            if not Preferences.getPluginManager("ActivateExternal"):
+                Preferences.setPluginManager("ActivateExternal", True)
+                self.__restartNeeded = True
             self.__closeButton.show()
             self.__cancelButton.hide()