GDC compile failure (gdc-5.2.0-1 arch linux)

[Laeeth]

laeeth@engine parsereddit]$ dub build --compiler=gdc
WARNING: A deprecated branch based version specification is used for the dependency fast. Please use numbered versions instead. Also note that you can still use the dub.selections.json file to override a certain dependency to use a branch instead.
Performing "debug" build using gdc for x86_64.
fast ~master: building configuration "library"...
parsereddit ~master: building configuration "application"...
/home/laeeth/.dub/packages/fast-master/source/fast/json.d: In member function 'skipWhitespace':
/home/laeeth/.dub/packages/fast-master/source/fast/parsing.d:661:6: error: inlining failed in call to always_inline 'skipAsciiWhitespace': function body not available
void skipAsciiWhitespace(ref const(char)* p)
^
/home/laeeth/.dub/packages/fast-master/source/fast/json.d:1336:4: error: called from here
m_text.skipAsciiWhitespace();
^
gdc failed with exit code 1.