SearchClient.Instance.Index throws error?

Hi Team,

We implemented find languagerouting for a custom index model.

indexItem.LanguageRouting = new LanguageRouting(Language.English);

When i try to index the model it throws an error.Like below 

   at EPiServer.Find.ClientConventions.CompositeLanguageRoutingConvention.GetLanguageRouting(Object instance)
   at EPiServer.Find.Client.Index(Object objectToIndex, Action`1 commandAction)
   at EPiServer.Find.Client.Index(Object objectToIndex)

Please help me out.

Regards,

Karthik

Edit:

Actually  i am using this method to set an languagrouting

                indexItem.LanguageRouting = new LanguageRouting(findclient.Settings.Languages.GetSupportedLanguage(language));