diff --git a/accessibility/mag/mag.1 b/accessibility/mag/mag.1
index 230168b011..060a3010f8 100644
--- a/accessibility/mag/mag.1
+++ b/accessibility/mag/mag.1
@@ -1,8 +1,5 @@
 .\" Man page generated from reStructuredText.
 .
-.TH MAG 1 "2020-11-01" "20100913" "SlackBuilds.org"
-.SH NAME
-mag \- dynamic X11 screen magnifier
 .
 .nr rst2man-indent-level 0
 .
@@ -30,6 +27,9 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
+.TH "MAG" 1 "2021-12-07" "20100913" "SlackBuilds.org"
+.SH NAME
+mag \- dynamic X11 screen magnifier
 .\" RST source for mag(1) man page. Convert with:
 .
 .\" rst2man.py mag.rst > mag.1
@@ -49,16 +49,16 @@ furthest corner away from the mouse. Without, you can grab it and move it as you
 .SH OPTIONS
 .INDENT 0.0
 .TP
-.B \-s
+.B  \-s
 small window.
 .TP
-.B \-m
+.B  \-m
 medium window.
 .TP
-.B \-l
+.B  \-l
 large window.
 .TP
-.B \-d
+.B  \-d
 Dynamic placement.
 .TP
 .BI \-z \ n
@@ -70,6 +70,10 @@ Original X placement.
 .BI \-y \ Ycoord
 Original Y placement.
 .UNINDENT
+.SH BUGS
+.sp
+There is no way to exit \fBmag\fP normally. Use e.g. \fBkillall mag\fP or
+\fBxkill\fP to force it to quit.
 .SH AUTHORS
 .sp
 mag was written by Danny Chouinard.
diff --git a/accessibility/mag/mag.SlackBuild b/accessibility/mag/mag.SlackBuild
index 470ddbc49a..c370bf6c47 100644
--- a/accessibility/mag/mag.SlackBuild
+++ b/accessibility/mag/mag.SlackBuild
@@ -8,11 +8,15 @@
 
 # VERSION comes from the last modified date on the homepage.
 
+# 20211207 bkw: BUILD=2
+# - fix blank window on -current (it shouldn't have worked on 14.2 either).
+# - add BUGS to man page (no way to exit mag).
+
 cd $(dirname $0) ; CWD=$(pwd)
 
 PRGNAM=mag
 VERSION=${VERSION:-20100913}
-BUILD=${BUILD:-1}
+BUILD=${BUILD:-2}
 TAG=${TAG:-_SBo}
 PKGTYPE=${PKGTYPE:-tgz}
 
@@ -54,7 +58,22 @@ set -e
 # In case you're wondering, -Wl,-s builds a stripped binary.
 rm -rf $PKG
 mkdir -p $PKG/usr/bin $OUTPUT
+
+cd $PKG
+
+# 20211207 bkw: we *do* have to patch it now, and we don't want
+# to write to $CWD, so:
+cat $CWD/$PRGNAM.c > $PRGNAM.c
+
+# 20211207 bkw: silly mistake in the code: it was calling
+# XDestroyImage(ximage) before the for loop that *uses* ximage.
+# On 14.2's X, this was equivalent to a use-after-free, and worked
+# accidentally most (or even all) of the time, but on -current's X,
+# it results in a blank (all-black) window.
+patch -p0 < $CWD/xdestroyimage.diff
+
 gcc $SLKCFLAGS -Wl,-s -o $PKG/usr/bin/$PRGNAM $PRGNAM.c -lX11
+rm $PRGNAM.c
 
 # Man page written by SlackBuild author. Please don't include mag.rst
 # in the package, it's the source for the man page only.
diff --git a/accessibility/mag/mag.rst b/accessibility/mag/mag.rst
index 1a8381b551..7e3c5c0f8a 100644
--- a/accessibility/mag/mag.rst
+++ b/accessibility/mag/mag.rst
@@ -43,6 +43,12 @@ OPTIONS
 -x Xcoord          Original X placement.                             
 -y Ycoord          Original Y placement.
 
+BUGS
+====
+
+There is no way to exit **mag** normally. Use e.g. **killall mag** or
+**xkill** to force it to quit.
+
 AUTHORS
 =======
 
diff --git a/accessibility/mag/xdestroyimage.diff b/accessibility/mag/xdestroyimage.diff
new file mode 100644
index 0000000000..1b4a0b8e11
--- /dev/null
+++ b/accessibility/mag/xdestroyimage.diff
@@ -0,0 +1,18 @@
+--- mag.c	2010-09-13 13:56:43.000000000 -0400
++++ mag.c.fixed	2021-12-07 23:23:49.729231259 -0500
+@@ -174,7 +174,6 @@
+       ximage=XGetImage(display,root,x-sx,y-sy,width/zoom,height/zoom,AllPlanes,ZPixmap);
+       // fprintf(stderr,"XGetImage returns:%d\n",(int)ximage);
+       // XPutImage(display,main_win,the_GC,ximage,0,0,0,0,width,height);
+-      XDestroyImage(ximage);
+       for(sx=0;sx<width/zoom;sx++) {
+         for(sy=0;sy<height/zoom;sy++) {
+           pix=XGetPixel(ximage,sx,sy);
+@@ -186,6 +185,7 @@
+           }
+         }
+       }
++      XDestroyImage(ximage);
+       XFlush(display);
+     } else {
+       usleep(30000);