Xamarin lost custom objc categories (unrecognized

The situation:

I have a custom category defined in my objc static library:

@implementation UIViewController (Colorful)
-(void)changeColor:(UIColor *)color
{
    self.view.backgroundColor = color;
}
@end

It is bind to Xamarin project:

[Category, BaseType(typeof(UIViewController))]
interface UIViewController_Colorful
{
    [Export ("changeColor:")]
    void ChangeColor(UIColor color);
}

This category is used in code like this:

public override bool FinishedLaunching (UIApplication app, NSDictionary options)
{
    window = new UIWindow (UIScreen.MainScreen.Bounds);

    UIViewController vc = new UIViewController ();
    vc.ChangeColor (UIColor.Red);
    window.RootViewController = vc;

    window.MakeKeyAndVisible ();

    return true;
}

It works fine on simulator, but on device I get following exception. Same situation appears even if category is called inside the library itself.

My setup is OS X 10.10, Xcode 6.3, Xamarin studio 5.9.3, Xamarin.iOS 8.10.1.64, Mono 4.0.1

Thanks.

$exception  {Foundation.MonoTouchException: Objective-C exception thrown.  Name: NSInvalidArgumentException Reason: -[UIViewController changeColor:]: unrecognized selector sent to instance 0x1759cd70
   at ObjCRuntime.Runtime.ThrowNSException (IntPtr ns_exception) [0x00000] in /Users/builder/data/lanes/1503/e6ebd18b/source/maccore/src/ObjCRuntime/Runtime.cs:167
   at ObjCRuntime.Runtime.throw_ns_exception (IntPtr exc) [0x00000] in <filename unknown>:0    
   at (wrapper native-to-managed) ObjCRuntime.Runtime:throw_ns_exception (intptr)   
   at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)   
   at UIKit.UIApplication.Main (System.String[] args, IntPtr principal, IntPtr delegate) [0x00005] in /Users/builder/data/lanes/1503/e6ebd18b/source/maccore/src/UIKit/UIApplication.cs:63    at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0001c] in /Users/builder/data/lanes/1503/e6ebd18b/source/maccore/src/UIKit/UIApplication.cs:46    
   at XTestApp.Application.Main (System.String[] args) [0x00008] in /Volumes/MacWork/xamarin/BindingTest/xamarin/XTest/XTestApp/Main.cs:17  

   NSInvalidArgumentException: -[UIViewController changeColor:]: unrecognized selector sent to instance 0x1759cd70  
   0   CoreFoundation                      0x264de007 <redacted> + 150  
   1   libobjc.A.dylib                     0x3478dc8b objc_exception_throw + 38     
   2   CoreFoundation                      0x264e3409 <redacted> + 0    
   3   CoreFoundation                      0x264e1327 <redacted> + 714  
   4   CoreFoundation                      0x26410e78 _CF_forwarding_prep_0 + 24    
   5   XTestApp                            0x0026e21c wrapper_managed_to_native_ApiDefinition_Messaging_void_objc_msgSend_IntPtr_intptr_intptr_intptr + 228     
   6   XTestApp                            0x0026d4c0 Binding_UIViewController_Colorful_ChangeColor_UIKit_UIViewController_UIKit_UIColor + 432  
   7   XTestApp                            0x000c8424 XTestApp_AppDelegate_FinishedLaunching_UIKit_UIApplication_Foundation_NSDictionary + 592  
   8   XTestApp                            0x0022c4d8 wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr + 224    
   9   XTestApp                            0x0029d933 mono_jit_runtime_invoke + 1190    
   10  XTestApp                            0x002da025 mono_runtime_invoke + 88  
   11  XTestApp                            0x0026e605 native_to_managed_trampoline_1 + 420  
   12  XTestApp                            0x0026ea31 -[AppDelegate application:didFinishLaunchingWithOptions:] + 100   
   13  UIKit                               0x29b9e293 <redacted> + 374  
   14  UIKit                               0x29d94b29 <redacted> + 2444     
   15  UIKit                               0x29d971e9 <redacted> + 1412     
   16  UIKit                               0x29da1e69 <redacted> + 36   
   17  UIKit                               0x29d9598b <redacted> + 130  
   18  FrontBoardServices                  0x2cf95ec9 <redacted> + 16   
   19  CoreFoundation                      0x264a3fd5 <redacted> + 12   
   20  CoreFoundation                      0x264a3299 <redacted> + 216  
   21  CoreFoundation                      0x264a1dd3 <redacted> + 1714     
   22  CoreFoundation                      0x263ee201 CFRunLoopRunSpecific + 476    
   23  CoreFoundation                      0x263ee013 CFRunLoopRunInMode + 106  
   24  UIKit                               0x29b97e67 <redacted> + 558  
   25  UIKit                               0x29b92a59 UIApplicationMain + 1440  
   26  XTestApp                            0x0010710c wrapper_managed_to_native_UIKit_UIApplication_UIApplicationMain_int_string___intptr_intptr + 272  
   27  XTestApp                            0x000e56dc UIKit_UIApplication_Main_string___intptr_intptr + 52  
   28  XTestApp                            0x000e569c UIKit_UIApplication_Main_string___string_string + 204     
   29  XTestApp                            0x000c8130 XTestApp_Application_Main_string__ + 172  
   30  XTestApp                            0x0022c4d8 wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr + 224    
   31  XTestApp                            0x0029d933 mono_jit_runtime_invoke + 1190    
   32  XTestApp                            0x002da025 mono_runtime_invoke + 88  
   33  XTestApp                            0x002dd4c7 mono_runtime_exec_main + 282  
   34  XTestApp                            0x002dd309 mono_runtime_run_main + 476   
   35  XTestApp                            0x0028c5d9 mono_jit_exec + 48    
   36  XTestApp                            0x0032d3ec xamarin_main + 2184   
   37  XTestApp                            0x0026f4dd main + 112    
   38  libdyld.dylib                       0x34d19aaf <redacted> + 2 }  Foundation.MonoTouchException

All static libraries containing Objective-C categories must pass -ObjC to the native linker, otherwise the categories may be removed (as documented by Apple).

This can be accomplished in two ways:

Adding -gcc_flags -ObjC to the additional mtouch arguments in the project's iOS Build options for every (device) project configuration.
If using a binding project, you can modify the LinkWith attribute to contain this linker flag:
```
[assembly: LinkWith ("...", LinkerFlags = "-ObjC")]
```