diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -399,8 +399,12 @@
 STARTTIME!= LC_ALL=C date
 CHECK_TIME!= cmp=`mktemp`; find ${.CURDIR}/sys/sys/param.h -newer "$$cmp" && rm "$$cmp"; echo
 .if !empty(CHECK_TIME)
+.if make(buildenv) && !defined(BUILDENV_SHELL)
+.warning check your date/time: ${STARTTIME}
+.else
 .error check your date/time: ${STARTTIME}
 .endif
+.endif
 
 .if defined(HISTORICAL_MAKE_WORLD) || defined(DESTDIR)
 #