Query fails if path contains white-space

[quazar0]

I am trying to query data from a 3d party RRD database, so I have no control over the name of the RRD files/paths. Some of the paths contain a space character. The grafana-rrd-server always returns a 500 status.
I've tried escaping the space with a backslash '\'.
And I've tried using the URL encoding '%20'.
And I've tried wrapping the entire name in double-quotes (").
Nothing seems to work.

Example target:
$testhost/os/interface/Ethernet 1_1/ifInOctets:ds0