diff --git a/share/mk/bsd.sys.mk b/share/mk/bsd.sys.mk
index 5bd8cd3362d..93e7c857231 100644
--- a/share/mk/bsd.sys.mk
+++ b/share/mk/bsd.sys.mk
@@ -321,12 +321,9 @@ SSP_CFLAGS?=	-fstack-protector-strong
 .endif
 CFLAGS+=	${SSP_CFLAGS}
 .endif # SSP
-
-.if empty(CFLAGS:M-D_FORTIFY_SOURCE*)
-CFLAGS+=	-D_FORTIFY_SOURCE=${FORTIFY_SOURCE.${.IMPSRC:T}:U${FORTIFY_SOURCE}}
-.endif
-.if empty(CXXFLAGS:M-D_FORTIFY_SOURCE*)
-CXXFLAGS+=	-D_FORTIFY_SOURCE=${FORTIFY_SOURCE.${.IMPSRC:T}:U${FORTIFY_SOURCE}}
+.if ${FORTIFY_SOURCE} > 0
+CFLAGS+=	-D_FORTIFY_SOURCE=${FORTIFY_SOURCE}
+CXXFLAGS+=	-D_FORTIFY_SOURCE=${FORTIFY_SOURCE}
 .endif
 
 # Additional flags passed in CFLAGS and CXXFLAGS when MK_DEBUG_FILES is