Index: share/mk/bsd.sys.mk
===================================================================
--- share/mk/bsd.sys.mk	(revision 308238)
+++ share/mk/bsd.sys.mk	(working copy)
@@ -117,7 +117,7 @@
 # How to handle FreeBSD custom printf format specifiers.
 .if ${COMPILER_TYPE} == "clang" && ${COMPILER_VERSION} >= 30600
 FORMAT_EXTENSIONS=	-D__printf__=__freebsd_kprintf__
-.else
+.elif !defined(WITHOUT_FORMAT_EXTENSIONS)
 FORMAT_EXTENSIONS=	-fformat-extensions
 .endif