--- a/client.mk
+++ b/client.mk
@@ -86,18 +86,24 @@ ifneq (,$(findstring mingw,$(CONFIG_GUES
 
 # check for CRLF line endings
 ifneq (0,$(shell $(PERL) -e 'binmode(STDIN); while (<STDIN>) { if (/\r/) { print "1"; exit } } print "0"' < $(TOPSRCDIR)/client.mk))
 $(error This source tree appears to have Windows-style line endings. To \
 convert it to Unix-style line endings, check \
 "https://developer.mozilla.org/en-US/docs/Developer_Guide/Mozilla_build_FAQ\#Win32-specific_questions" \
 for a workaround of this issue.)
 endif
+
+# Set this for baseconfig.mk
+HOST_OS_ARCH=WINNT
 endif
 
+# Include baseconfig.mk for its $(MAKE) validation.
+include $(TOPSRCDIR)/config/baseconfig.mk
+
 ####################################
 # Load mozconfig Options
 
 # See build pages, http://www.mozilla.org/build/ for how to set up mozconfig.
 
 define CR