Map exception only on device (iOS)

Hi all,
I'm using a Map with pins in a NavigationPage. When I go to previous page I get an exception:
Unhandled managed exception: Objective-C exception thrown. Name: NSInternalInconsistencyException Reason: An instance 0x175f45e0 of class MKPointAnnotation was deallocated while key value observers were still registered with it. Current observation info: (
Context: 0x0, Property: 0x1744d210>
) (Foundation.MonoTouchException)
at ObjCRuntime.Runtime.ThrowNSException (IntPtr ns_exception) [0x00000] in /Developer/MonoTouch/Source/maccore/src/ObjCRuntime/Runtime.cs:156
at ObjCRuntime.Runtime.throw_ns_exception (IntPtr exc) [0x00000] in :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 /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:62
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0001c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:45
at AbruzzoByNight.iOS.Application.Main (System.String[] args) [0x00008] in /Users/fabiomarcone/progetti/ABNXamarin/AbruzzoByNight/iOS/Main.cs:17

I've no error using simulator. I can't test it in a Android device...

Do I have to open a bug?

Thanks.
Fabio