Building a NodeJS addon with mixed C/C++ source files

I'm trying to build a NodeJS addon from mixed C/C++ source. I want to avoid building the C code as separate shared library, though this is a partial solution.

I get the error:

Cannot guess how to process src:///home/chris/Dropbox/cbackend/data.c 
(got mappings ['.C', '.cc', '.cpp', '.c++', '.cxx'] 
in <class 'cxx.cxx_taskgen'>) -> try conf.check_tool(..)?

when I try to build it. If I rename the .c file as .cc and change the wscript appropriately it all work fine.

I've tried adding a 'compiler_c' to the wscript, but it doesn't seem to be available.

Here's the wscript:

import os
import Options

srcdir = '.'
blddir = 'build'
VERSION = '0.3.0'

def set_options(opt):
  opt.tool_options('compiler_cxx')

def configure(conf):
  conf.check_tool('compiler_cxx')
  conf.check_tool('node_addon')

  conf.env.append_value('CCFLAGS', ['-O3'])
  conf.env.append_value('CXXFLAGS', ['-O3'])
  if Options.platform == 'darwin': conf.env.append_value('LINKFLAGS', ['-undefined', 'dynamic_lookup'])

def build(bld):
  obj = bld.new_task_gen('cxx', 'shlib', 'node_addon')
  obj.target = 'cbackend'
  obj.source = 'cbackend.cc data.c'
  obj.uselib = ['NODE']