TeamCity "Can't load types from xmlns"

I have a problem. Everything is fine when I build my project locally but on TeamCity it fails with this error:

C:\TeamCity\buildAgent\work\c0a48cbf39acc960\packages\Xamarin.Forms.1.2.3.6257\build\portable-win+net45+wp80+MonoAndroid10+MonoTouch10\Xamarin.Forms.targets(16, 3): error MSB4018: The "XamlG" task failed unexpectedly.
System.Exception: Can't load types from xmlns clr-namespace:MyNamespace.Controls;assembly=MyAssembly
at Xamarin.Forms.Build.Tasks.XamlG.GetNamespace(String namespaceuri)
at Xamarin.Forms.Build.Tasks.XamlG.GetType(String nsuri, String type, IList1 typeArguments, Func2 getNamespaceOfPrefix)
at Xamarin.Forms.Build.Tasks.XamlG.GetNamesAndTypes(XmlNode root, XmlNamespaceManager nsmgr)
at Xamarin.Forms.Build.Tasks.XamlG.GenerateFile(String xamlFile, String outFile)
at Xamarin.Forms.Build.Tasks.XamlG.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.d__20.MoveNext()

What could be a problem in this case?
Thank you!