HTTP headers for chunked encoding POST - Error 411

I'm sending data to a server with an Arduino which requires constructing an HTML POST line-by-line. I don't necessarily know the Content-Length a-priori, so I am using "chunked" encoding.

When I tried this example post from Wikipedia with the "Transfer-Encoding" option as specified in rfc2616

client.println("POST /myurl HTTP/1.1"); client.println("Host: 12.345.679.999"); // replaced with the test server's IP client.println("User-Agent: Arduino/1.0"); client.println("Transfer-Encoding: chunked"); client.println(); client.println("4"); client.println("test"); client.println("0"); client.println(); 

or, with escape characters explicit:

client.print("4\r\ntest\r\n0\r\n\r\n"); 

I receive the error from my server:

HTTP/1.1 411 Length Required A request of the requested method POST requires a valid Content-length. Server: Apache/2.2.22 (Ubuntu) 

However, "chunked" encoding shouldn't require a Content-Length header field, see 4.4 - Message Length in rfc2616

Am I missing a field? Why doesn't this call work?

For the record, the non-Chunked-Encoding works:

if(client.connect(server, 80)){ String PostData = "test"; Serial.println("POST /myurl HTTP/1.1"); client.println("Host: 12.345.679.999"); // replaced with the test server's IP Serial.println("User-Agent: Arduino/1.0"); Serial.print("Content-Length: "); Serial.println(PostData.length()); Serial.println(); Serial.println(PostData); } 

UPDATE

From the apache2 error.log: "chunked Transfer-Encoding forbidden"