ASIHTTPRequest coding problems

I use in the project ASIHTTPRequest, often encounter the following link error:

Incorrect NSStringEncoding value 0x0000 detected. Assuming NSASCIIStringEncoding. Will stop this compatiblity mapping behavior in the near future.

Some websites say that coding problem, but does not know how to solve.

Does not always happen, but the frequency is very high.
Reply:
request.defaultResponseEncoding = NSUTF8StringEncoding;
Add the phrase seemed to have never met a coding error.