diff --git a/Mk/Uses/display.mk b/Mk/Uses/display.mk
index b5471b95a8ce..ac6b0cc97ee1 100644
--- a/Mk/Uses/display.mk
+++ b/Mk/Uses/display.mk
@@ -1,52 +1,58 @@
 # Feature:	display
 # Usage:	USES=display or USES=display:ARGS
 # Valid ARGS:	install (default, implicit), configure, build
 # 
 # Except the target where the DISPLAY is needed
 #
 # MAINTAINER: x11@FreeBSD.org
 
 .if !defined(_INCLUDE_USES_DISPLAY_MK)
 _INCLUDE_USES_DISPLAY_MK=	yes
 
 .  if empty(display_ARGS)
 display_ARGS=	install
 .  endif
 
 .  if !defined(DISPLAY)
 
 .    if ${display_ARGS:Mconfigure}
 DISPLAY_DEPENDS=	BUILD_DEPENDS
 CONFIGURE_ENV+=		DISPLAY=":${XVFBPORT}"
 .    elif ${display_ARGS:Mbuild}
 DISPLAY_DEPENDS=	BUILD_DEPENDS
 MAKE_ENV+=		DISPLAY=":${XVFBPORT}"
 .    elif ${display_ARGS:Mtest}
 DISPLAY_DEPENDS=	TEST_DEPENDS
 TEST_ENV+=		DISPLAY=":${XVFBPORT}"
 .else
 IGNORE=			USES=display: invalid arguments: ${display_ARGS}
 .endif
 
 ${DISPLAY_DEPENDS}+= \
 	Xvfb:x11-servers/xorg-server@xvfb \
 	${LOCALBASE}/share/fonts/misc/8x13O.pcf.gz:x11-fonts/xorg-fonts-miscbitmaps \
 	${LOCALBASE}/share/fonts/misc/fonts.alias:x11-fonts/font-alias \
 	${LOCALBASE}/share/X11/xkb/rules/base:x11/xkeyboard-config \
 	xkbcomp:x11/xkbcomp
 
 XVFBPORT?=	0
 XVFBPIDFILE=	/tmp/.xvfb-${XVFBPORT}-display-mk.pid
 
 .    for t in ${display_ARGS}
 _USES_${t}+=	290:start-display 860:stop-display
 .    endfor
 start-display:
 	pkill -15 -F ${XVFBPIDFILE} || ${TRUE}
 	daemon -p ${XVFBPIDFILE} Xvfb :${XVFBPORT}
 
 stop-display:
 	pkill -15 -F ${XVFBPIDFILE}
 
+.  else
+# DISPLAY is already defined, which means we're running in an existing session
+TEST_ENV+=		DISPLAY="${DISPLAY}"
+.    if defined(XAUTHORITY)
+TEST_ENV+=		XAUTHORITY="${XAUTHORITY}"
+.    endif
 .  endif
 .endif