A lighting device including a glass tube; a solid state lighting assembly in said glass tube, said assembly including an electrically insulating optical film having at least one arcuate portion lining a part of the inner surface of the glass tube, wherein the glass tube includes a further part defining a light exit portion; and a plurality of solid state lighting elements on a carrier, said carrier contacting said optical film; a thermally conductive member in between at least a part of the solid state lighting assembly and the glass tube for thermally coupling the solid state lighting elements to the glass tube; and a transparent or translucent electrically insulating cover contacting the electrically insulating optical film and covering the solid state lighting elements. A luminaire including such a lighting device and a lighting device assembly method are also disclosed.