diff --git a/man2/mlock.2 b/man2/mlock.2
index 535a7db1b..8afef4b3c 100644
--- a/man2/mlock.2
+++ b/man2/mlock.2
@@ -24,7 +24,7 @@
 .\" Software Foundation, Inc., 59 Temple Place, Suite 330,
 .\" Boston, MA 02111, USA.
 .\"
-.TH MLOCK 2 2011-09-10 "Linux" "Linux Programmer's Manual"
+.TH MLOCK 2 2011-09-14 "Linux" "Linux Programmer's Manual"
 .SH NAME
 mlock, munlock, mlockall, munlockall \- lock and unlock memory
 .SH SYNOPSIS
@@ -157,8 +157,11 @@ and
 Some or all of the specified address range could not be locked.
 .TP
 .B EINVAL
-.I len
-was negative.
+The result of the addition
+.IR start + len
+was less than
+.IR start 
+(e.g., the addition may have resuled in an overflow).
 .TP
 .B EINVAL
 (Not on Linux)