--- old/make/Main.gmk	2017-10-05 11:55:54.748863624 +0200
+++ new/make/Main.gmk	2017-10-05 11:55:54.496867603 +0200
@@ -51,7 +51,7 @@
 ALL_TARGETS :=
 
 # Hook to include the corresponding custom file, if present.
-$(eval $(call IncludeCustomExtension, , Main.gmk))
+$(eval $(call IncludeCustomExtension, Main.gmk))
 
 # All modules for the current target platform.
 ALL_MODULES := $(call FindAllModules)