‘Microsoft.Web.Services2.SoapEnvelope’ must be Xml serializable to be a message part type — check event log for more information

I am trying to send a message of type Microsoft.Web.Services2.SoapEnvelope from Biztalk and I am recieving this error.

I am using a .net class library that reurns SoapEnvelope to Biztalk Message.

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Failed to Xml serialize type ‘Microsoft.Web.Services2.SoapEnvelope’.
       
Exception type: XmlSerializationException
Additional error information:

        Cannot use wildcards at the top level of a schema.
       
Exception type: InvalidOperationException
Source: System.Xml
Target Site: System.Xml.Schema.XmlSchemaElement ExportElement(System.Xml.Serialization.ElementAccessor)
The following is a stack trace that identifies the location where the exception occured

   at System.Xml.Serialization.XmlSchemaExporter.ExportElement(ElementAccessor accessor)
   at System.Xml.Serialization.XmlSchemaExporter.ExportTypeMapping(XmlTypeMapping xmlTypeMapping)
   at Microsoft.XLANGs.RuntimeTypes.DotNetTypeMetadata.get_XmlSchema()
   at Microsoft.XLANGs.RuntimeTypes.CompilerMetaDataInfo.GetPropertiesForDotNetPartType(String typeName, String assemblyLocation, String& formatterTypeName, String& reflectedTypeName, String& targetNameSpace)