AxiomSoapMessageFactory does not parse application/xop+xml Content-Type properly

AxiomSoapMessageFactory#getCharSetEncoding(), when given the following HTTP Content-Type header (which I assume is valid),

application/xop+xml;type="text/xml; charset=utf-8"

returns a CharSet of 'utf-8"' instead of 'utf-8' (i.e. there is an erroneous double quote at the end of the string).