diff --git a/sys/src/cmd/cat.c b/sys/src/cmd/cat.c
index ac5888979..83d080f98 100644
--- a/sys/src/cmd/cat.c
+++ b/sys/src/cmd/cat.c
@@ -7,7 +7,7 @@ cat(int f, char *s)
 	char buf[8192];
 	long n;
 
-	while((n=read(f, buf, (long)sizeof buf))>0)
+	while((n=read(f, buf, sizeof buf))>0)
 		if(write(1, buf, n)!=n)
 			sysfatal("write error copying %s: %r", s);
 	if(n < 0)