--- a/MozillaFirefox/MozillaFirefox.spec	Thu Jan 11 10:37:42 2018 +0100
+++ b/MozillaFirefox/MozillaFirefox.spec	Thu Jan 11 16:29:08 2018 +0100
@@ -373,7 +373,7 @@
 ac_add_options --disable-webrtc
 %endif
 EOF
-make -f client.mk build
+./mach build
 
 %install
 cd $RPM_BUILD_DIR/obj