--- Libc/Libc-320/gen/sigsetops.c
+++ Libc/Libc-583/gen/sigsetops.c
@@ -2,8 +2,6 @@
  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
  *
  * @APPLE_LICENSE_HEADER_START@
- * 
- * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
  * 
  * This file contains Original Code and/or Modifications of Original Code
  * as defined in and that are subject to the Apple Public Source License
@@ -90,6 +88,8 @@
 		errno = EINVAL;
 		return(-1);
 	}
+	if (signo == 0)
+		return(0);
 	*set |= sigmask(signo);
 	return (0);
 }
@@ -103,6 +103,8 @@
 		errno = EINVAL;
 		return(-1);
 	}
+	if (signo == 0)
+		return(0);
 	*set &= ~sigmask(signo);
 	return (0);
 }
@@ -116,5 +118,7 @@
 		errno = EINVAL;
 		return(-1);
 	}
+	if (signo == 0)
+		return(0);
 	return ((*set & sigmask(signo)) != 0);
 }