drafter: Error while building master on MacOS

/Applications/Xcode.app/Contents/Developer/usr/bin/make -C ./build V=1 drafter
  c++ '-DBUILDING_DRAFTER=1' '-D_DARWIN_USE_64_BIT_INODE=1' '-DDRAFTER_BUILD_STATIC' -I../ext/boost_1_66_0 -I../ext/sos/src -I../ext/snowcrash/src -I../ext/snowcrash/ext/markdown-parser/src -I../ext/snowcrash/ext/markdown-parser/ext/sundown/src  -Os -gdwarf-2 -mmacosx-version-min=10.7 -arch x86_64 -Wall -Wendif-labels -W -Wno-unused-parameter -std=c++14 -stdlib=libc++ -fno-threadsafe-statics -fno-strict-aliasing -MMD -MF out/Release/.deps/out/Release/obj.target/libdrafter/src/drafter.o.d.raw   -c -o out/Release/obj.target/libdrafter/src/drafter.o ../src/drafter.cc
  c++ '-DBUILDING_DRAFTER=1' '-D_DARWIN_USE_64_BIT_INODE=1' '-DDRAFTER_BUILD_STATIC' -I../ext/boost_1_66_0 -I../ext/sos/src -I../ext/snowcrash/src -I../ext/snowcrash/ext/markdown-parser/src -I../ext/snowcrash/ext/markdown-parser/ext/sundown/src  -Os -gdwarf-2 -mmacosx-version-min=10.7 -arch x86_64 -Wall -Wendif-labels -W -Wno-unused-parameter -std=c++14 -stdlib=libc++ -fno-threadsafe-statics -fno-strict-aliasing -MMD -MF out/Release/.deps/out/Release/obj.target/libdrafter/src/Serialize.o.d.raw   -c -o out/Release/obj.target/libdrafter/src/Serialize.o ../src/Serialize.cc
  c++ '-DBUILDING_DRAFTER=1' '-D_DARWIN_USE_64_BIT_INODE=1' '-DDRAFTER_BUILD_STATIC' -I../ext/boost_1_66_0 -I../ext/sos/src -I../ext/snowcrash/src -I../ext/snowcrash/ext/markdown-parser/src -I../ext/snowcrash/ext/markdown-parser/ext/sundown/src  -Os -gdwarf-2 -mmacosx-version-min=10.7 -arch x86_64 -Wall -Wendif-labels -W -Wno-unused-parameter -std=c++14 -stdlib=libc++ -fno-threadsafe-statics -fno-strict-aliasing -MMD -MF out/Release/.deps/out/Release/obj.target/libdrafter/src/SerializeResult.o.d.raw   -c -o out/Release/obj.target/libdrafter/src/SerializeResult.o ../src/SerializeResult.cc
../src/SerializeResult.cc:88:12: error: no viable conversion from returned value of type 'unique_ptr<refract::Element<refract::dsd::Array>, default_delete<refract::Element<refract::dsd::Array>>>' to
      function return type 'unique_ptr<refract::IElement, default_delete<refract::IElement>>'
    return parseResult;
           ^~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:2553:29: note: candidate constructor (the implicit copy constructor) not viable: no known
      conversion from 'std::__1::unique_ptr<refract::Element<refract::dsd::Array>, std::__1::default_delete<refract::Element<refract::dsd::Array> > >' to 'const std::__1::unique_ptr<refract::IElement,
      std::__1::default_delete<refract::IElement> > &' for 1st argument
class _LIBCPP_TYPE_VIS_ONLY unique_ptr
                            ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:2582:49: note: candidate constructor not viable: no known conversion from
      'std::__1::unique_ptr<refract::Element<refract::dsd::Array>, std::__1::default_delete<refract::Element<refract::dsd::Array> > >' to 'nullptr_t' for 1st argument
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT
                                                ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:2609:31: note: candidate constructor not viable: no known conversion from
      'std::__1::unique_ptr<refract::Element<refract::dsd::Array>, std::__1::default_delete<refract::Element<refract::dsd::Array> > >' to 'std::__1::unique_ptr<refract::IElement,
      std::__1::default_delete<refract::IElement> > &&' for 1st argument
    _LIBCPP_INLINE_VISIBILITY unique_ptr(unique_ptr&& __u) _NOEXCEPT
                              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:2613:9: note: candidate constructor [with _Up = refract::Element<refract::dsd::Array>, _Ep
      = std::__1::default_delete<refract::Element<refract::dsd::Array> >] not viable: no known conversion from 'std::__1::unique_ptr<refract::Element<refract::dsd::Array>,
      std::__1::default_delete<refract::Element<refract::dsd::Array> > >' to 'unique_ptr<refract::Element<refract::dsd::Array>, std::__1::default_delete<refract::Element<refract::dsd::Array> > > &&' for
      1st argument
        unique_ptr(unique_ptr<_Up, _Ep>&& __u,
        ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/memory:2628:35: note: candidate template ignored: could not match 'auto_ptr' against 'unique_ptr'
        _LIBCPP_INLINE_VISIBILITY unique_ptr(auto_ptr<_Up>&& __p,
                                  ^
1 error generated.
make[1]: *** [out/Release/obj.target/libdrafter/src/SerializeResult.o] Error 1
make: *** [drafter] Error 2

MacOS X 10.12.6