diff --git a/Makefile.inc1 b/Makefile.inc1
index f3c05a949084..54e6fefffe66 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -752,14 +752,20 @@ KMAKE=		${KMAKEENV} ${MAKE} ${.MAKEFLAGS} ${KERNEL_FLAGS} KERNEL=${INSTKERNNAME}
 # Attempt to rebuild the entire system, with reasonable chance of
 # success, regardless of how old your existing system is.
 #
-_sanity_check: .PHONY
+_sanity_check: .PHONY .MAKE
 .if ${.CURDIR:C/[^,]//g} != ""
 #	The m4 build of sendmail files doesn't like it if ',' is used
 #	anywhere in the path of it's files.
 	@echo
 	@echo "*** Error: path to source tree contains a comma ','"
 	@echo
-	false
+	@false
+.elif ${.CURDIR:M*\:*} != ""
+#	Using ':' leaks into PATH and breaks finding cross-tools.
+	@echo
+	@echo "*** Error: path to source tree contains a colon ':'"
+	@echo
+	@false
 .endif
 
 _worldtmp: .PHONY