Unable to find mscorlib, Version=4.0.0.0

I have a visual studio package which I compile in Visual Studio 2015 against .NET Framework 4.0. I have a single version of the package, which is compatible with Visual Studio 2010, 2012, 2013 and 2015.

A user has reported an exception

System.Runtime.Serialization.SerializationException

No se puede encontrar el ensamblado 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]], mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'

with the following stack trace

   en System.Runtime.Serialization.Formatters.Binary.BinaryAssemblyInfo.GetAssembly()
   en System.Runtime.Serialization.Formatters.Binary.ObjectReader.GetType(BinaryAssemblyInfo assemblyInfo, String name)
   en System.Runtime.Serialization.Formatters.Binary.ObjectMap..ctor(String objectName, String[] memberNames, BinaryTypeEnum[] binaryTypeEnumA, Object[] typeInformationA, Int32[] memberAssemIds, ObjectReader objectReader, Int32 objectId, BinaryAssemblyInfo assemblyInfo, SizedArray assemIdToAssemblyTable)
   en System.Runtime.Serialization.Formatters.Binary.__BinaryParser.ReadObjectWithMapTyped(BinaryObjectWithMapTyped record)
   en System.Runtime.Serialization.Formatters.Binary.__BinaryParser.ReadObjectWithMapTyped(BinaryHeaderEnum binaryHeaderEnum)
   en System.Runtime.Serialization.Formatters.Binary.__BinaryParser.Run()
   en System.Runtime.Serialization.Formatters.Binary.ObjectReader.Deserialize(HeaderHandler handler, __BinaryParser serParser, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage)
   en System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Deserialize(Stream serializationStream, HeaderHandler handler, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage)
   en System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Deserialize(Stream serializationStream)
   en System.Resources.ResXDataNode.GenerateObjectFromDataNodeInfo(DataNodeInfo dataNodeInfo, ITypeResolutionService typeResolver)
   en System.Resources.ResXDataNode.GetValue(ITypeResolutionService typeResolver)
   en MultiLang.clsResXUtil.ExportToResxSingleCulture(String ResXFileName, String CompName, String IetfTag, Boolean CleanUpResourceStrings, Set`1 DeletedResources)

The Windows version is "Microsoft Windows NT 10.0.10586.0" and the Visual Studio Version is "14.0.0.0", i.e
Windows 10 and Visual Studio 2015.
Is it possible that the user simply does not have .NET Framework 4.0 installed on the machine?
If so, does this invalidate the whole idea of having a single VS package for multiple versions of Visual Studio?
Phil