diff --git a/deskutils/sliderule/Makefile b/deskutils/sliderule/Makefile
index 2d22946ff3ab..01d412c294c0 100644
--- a/deskutils/sliderule/Makefile
+++ b/deskutils/sliderule/Makefile
@@ -1,16 +1,16 @@
 PORTNAME=	sliderule
 PORTVERSION=	1.0
-PORTREVISION=	11
+PORTREVISION=	12
 CATEGORIES=	deskutils
 MASTER_SITES=	LOCAL/joerg
 DISTNAME=	${PORTNAME}
 
 MAINTAINER=	joerg@FreeBSD.org
 COMMENT=	The part of X11R3's xcalc featuring a slide rule
 
 USES=		imake xorg
 USE_XORG=	x11 xext
 USE_GCC=	yes
 PLIST_FILES=	bin/sliderule share/man/man1/sliderule.1.gz
 
 .include <bsd.port.mk>
diff --git a/deskutils/sliderule/files/patch-xcalc.c b/deskutils/sliderule/files/patch-xcalc.c
new file mode 100644
index 000000000000..40bd7648d71f
--- /dev/null
+++ b/deskutils/sliderule/files/patch-xcalc.c
@@ -0,0 +1,19 @@
+--- xcalc.c.orig
++++ xcalc.c
+@@ -32,6 +32,7 @@
+  *                  it's an option.
+  */
+ 
++#include <errno.h>
+ #include <stdio.h>
+ #include <math.h>
+ #include <signal.h>
+@@ -43,8 +44,6 @@
+ 
+ /* program icon */
+ #include "icon"
+-
+-extern int errno;
+ 
+ 
+ /* constants used for setting up the calculator.  changing them would