@m-baumgartner : the ContentType is commented out on purpose. Did you read the comment in the source code? "RLebeau 8/13/2015: no longer setting a default ContentType here. Doing so sets a default CharSet, which would get carried over if the user assigns a new non-text ContentType without an explicit charset. TAppResponse does not expose access to the FResponseInfo.CharSet property. For example, if the user sets TAppResponse.ContentType to 'image/jpeg', the resulting Content-Type header woud be 'image/jpeg; charset=ISO-8859-1', which can cause problems for some clients. Besides, TIdHTTPResponseInfo.WriteHeader() sets the ContentType to 'text/html; charset=ISO-8859-1' if no ContentType has been provided but there is ContentText/ContentStream data, so this is redundant here anyway..." If you want your response to use a specific charset, set a ContentType that includes a charset attribute, ie:
Response.ContentType := 'text/json; charset=utf-8, though you really should be using
application/json, which does not have a charset attribute. If TDSJsonResponseHandler is having a problem handling this, then that is an Embarcadero issue.