QGIS » QGIS Application

After upgrading to Ubuntu 17.10 and installing the default QGis server from the repository, the WMS getLegendGraphics request parameter LAYERTITLE now produces wrong / different result.

There are 2 kinds of layers:
1. layers with multiple symbols (classes)
2. layers with a single symbol

Old (expected) behavior of the LAYERTITLE option in the WMS getLegendGraphics request:
layertitle=false => show only symbol names. If the layer has only one symbol, show the symbol name (by default identical to layer title)
layertitle=true => for layers with more than one symbol, show the layer title at the top of the list of symbols

New (unexpected) behavior:
layertitle=false => (see attached image legendlayertitlefalse.png): no names for single symbol layers, symbol names for multi-symbol layers
layertitle=true => (see attached image legendlayertitletrue.png): duplicate names for single symbol layers (layer-title + layer-title for single symbol), for multi-symbol layer: layer-title + symbol names for each symbol

Example WMS getLegendGraphics URLs:
laytertitle=false:
https://pico.geodan.nl/cgi-bin/qgis_mapserv.fcgi?DPI=120&map=/usr/lib/cgi-bin/projects/Infra_elektra_fout.qgs&request=GetLegendGraphic&service=WMS&itemFONTSIZE=8&format=png&layertitle=false&layer=Infra_elektra_fout

layertitle=true:
https://pico.geodan.nl/cgi-bin/qgis_mapserv.fcgi?DPI=120&map=/usr/lib/cgi-bin/projects/Infra_elektra_fout.qgs&request=GetLegendGraphic&service=WMS&itemFONTSIZE=8&format=png&layertitle=true&layer=Infra_elektra_fout