Got this error upon building from latest inbound on Linux. 0:18.81 Reticulating splines... 0:18.88 Traceback (most recent call last): 0:18.88 File "./config.status", line 956, in <module> 0:18.88 config_status(**args) 0:18.88 File "/media/dev/firefox/build/ConfigStatus.py", line 126, in config_status 0:18.88 summary = backend.consume(definitions) 0:18.88 File "/media/dev/firefox/python/mozbuild/mozbuild/backend/base.py", line 188, in consume 0:18.88 for obj in objs: 0:18.88 File "/media/dev/firefox/python/mozbuild/mozbuild/frontend/emitter.py", line 77, in emit 0:18.88 for o in self.emit_from_sandbox(out): 0:18.88 File "/media/dev/firefox/python/mozbuild/mozbuild/frontend/emitter.py", line 134, in emit_from_sandbox 0:18.88 % (symbol, src, sandbox['RELATIVEDIR'])) 0:18.88 mozbuild.frontend.reader.SandboxValidationError: Reference to a file that doesn't exist in CSRCS (arena.c) in memory/jemalloc 0:18.90 *** Fix above errors and then restart with "/usr/bin/make -f client.mk build" 0:18.90 make[2]: *** [configure] Error 1 0:18.90 make[1]: *** [/media/dev/firefox/obj/Makefile] Error 2 0:18.90 make: *** [build] Error 2 0:18.94 0 compiler warnings present. Still happens if the build is clobbered using |mach clobber|. Seems related to Bug 912438. My MOZCONFIG has --enable-jemalloc.