Language-Attribute (lang) and Retweets


I am currently tracking some keywords, hashtags and users with the StreamApi.
I noticed, that the language attribute (lang) of every tweet; that has been retweeted, is set to NULL.
Is this a bug or a feature to detect retweets?


I found the same problem. As a workaround: is there any way to ask for tweets without language?

I mean something like: lang=en,es,und with “und” meaning that i want the tweets with no language defined.

Thanks in advance.