Whitespace in PNG texts gets corrupted in image reading

I am trying to embed some XML data in a PNG image using QImage:: text and SetText APIs.

The text is of the form key=value where my key is "comment" and value is my xml data. The APIs works until the length of my xml data string reaches ~49. After that, nothing is inserted.

I looked into the PNG specification. Seems the spec itself does not impose any restriction on the length of the value. Only the key length is limited to 79 bytes. (http://www.w3.org/TR/PNG/#11tEXt).