diff -Nru /n/sources/plan9/sys/src/libmemdraw/write.c /sys/src/libmemdraw/write.c
--- /n/sources/plan9/sys/src/libmemdraw/write.c	Thu Feb 28 21:03:37 2002
+++ /sys/src/libmemdraw/write.c	Sun Nov  6 00:00:00 2016
@@ -64,7 +64,7 @@
 		if(nb != dy*bpl)
 			goto ErrOut;
 	}
-	sprint(hdr, "compressed\n%11s %11d %11d %11d %11d ",
+	snprint(hdr, sizeof hdr, "compressed\n%11s %11d %11d %11d %11d ",
 		chantostr(cbuf, i->chan), r.min.x, r.min.y, r.max.x, r.max.y);
 	if(write(fd, hdr, 11+5*12) != 11+5*12)
 		goto ErrOut;
@@ -170,7 +170,7 @@
 		if(loutp == outbuf)
 			goto ErrOut;
 		n = loutp-outbuf;
-		sprint(hdr, "%11d %11ld ", r.max.y, n);
+		snprint(hdr, sizeof hdr, "%11d %11ld ", r.max.y, n);
 		write(fd, hdr, 2*12);
 		write(fd, outbuf, n);
 		r.min.y = r.max.y;