Clean Unused Framework Libraries doesn't work

[lassana]

VS for Mac 8.1.5 (build 9): "Clean Unused Framework Libraries" does nothing, in the logs I found this:

ERROR [2019-07-12 11:19:24Z]: Error while executing command: Clear Unused Framework Libraries
System.MissingMethodException: Method not found: MonoDevelop.Ide.Gui.ProgressMonitorManager MonoDevelop.Ide.Gui.Workbench.get_ProgressMonitors()
  at MonoDevelop.Components.Commands.CommandHandler.Run (System.Object dataItem) [0x00000] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.Commands/CommandHandler.cs:75 
  at MonoDevelop.Components.Commands.CommandHandler.InternalRun (System.Object dataItem) [0x00000] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.Commands/CommandHandler.cs:39 
  at MonoDevelop.Components.Commands.CommandManager.DefaultDispatchCommand (MonoDevelop.Components.Commands.ActionCommand cmd, MonoDevelop.Components.Commands.CommandInfo info, System.Object dataItem, System.Object target, MonoDevelop.Components.Commands.CommandSource source) [0x0006e] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.Commands/CommandManager.cs:1637 
  at MonoDevelop.Components.Commands.CommandManager.DispatchCommand (System.Object commandId, System.Object dataItem, System.Object initialTarget, MonoDevelop.Components.Commands.CommandSource source, System.Nullable`1[T] time, MonoDevelop.Components.Commands.CommandInfo sourceUpdateInfo) [0x003b5] in /Users/vsts/agent/2.153.2/work/1/s/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components.Commands/CommandManager.cs:1600