"Open documentation" - environment variable not working

I used to use relative paths to access documentation files in eeschema. After recent changes in accessing doc files it doesn't work.
I tried to use environment variables KICAD_SYMBOL_DIR or KIPRJMOD to avoid putting absolute paths in libraries. I noticed that when I put component to the schematic, open Component Properties and click Show Datasheet then the documentation file opens (datasheet field value filled with path $KIPRJMOD/doc/Datasheets/Diodes/1N4007-E3_54.pdf) but when I try to open documentation from the components context menu then I get message:
Doc File '$KIPRJMOD/doc/Datasheets/Diodes/1N4007-E3_54.pdf' not found

version 201710311449+05ab44f~61~ubuntu14.04.1

Application: kicad
Version: no-vcs-found-05ab44f~61~ubuntu14.04.1, release build
Libraries:
    wxWidgets 3.0.2
    libcurl/7.35.0 OpenSSL/1.0.1f zlib/1.2.8 libidn/1.28 librtmp/2.3
Platform: Linux 3.19.0-32-generic x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.2 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
    Boost: 1.54.0
    Curl: 7.35.0
    Compiler: GCC 4.8.4 with C++ ABI 1002

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_SPICE=ON