diff --git a/gnu/usr.bin/cc/Makefile.inc b/gnu/usr.bin/cc/Makefile.inc
index 093b8ff7fcf..153872f521e 100644
--- a/gnu/usr.bin/cc/Makefile.inc
+++ b/gnu/usr.bin/cc/Makefile.inc
@@ -58,4 +58,8 @@ LIBCC_DRV=	${.CURDIR}/../cc_drv/libcc_drv.a
 
 LIBCC_INT=	${LIBDESTDIR}/libcc_int.a
 
+.if !defined(OSVERSION)
+OSVERSION!=	sysctl -n kern.osreldate
+.endif
+
 .endif # !GCCDIR