Index: Mk/bsd.port.mk
===================================================================
--- Mk/bsd.port.mk
+++ Mk/bsd.port.mk
@@ -1148,6 +1148,15 @@
 .endif
 _EXPORTED_VARS+=	ARCH
 
+# Get operating system versions for a cross build
+.if defined(CROSS_SYSROOT)
+.if !exists(${CROSS_SYSROOT}/usr/include/sys/param.h)
+.error CROSS_SYSROOT does not include /usr/include/sys/param.h.
+.endif
+OSVERSION!=	${AWK} '/^\#define[[:blank:]]__FreeBSD_version/ {print $$3}' < ${CROSS_SYSROOT}/usr/include/sys/param.h
+_OSRELEASE!= ${AWK} -v version=${OSVERSION} 'END { printf("%d.%d-CROSS", version / 100000, version / 1000 % 100) }' < /dev/null
+.endif
+
 # Get the operating system type
 .if !defined(OPSYS)
 OPSYS!=	${UNAME} -s