diff --git a/man2/dup.2 b/man2/dup.2
index 0daff0799..dba82a66c 100644
--- a/man2/dup.2
+++ b/man2/dup.2
@@ -33,7 +33,7 @@
 .\"     details for dup2().
 .\" 2008-10-09, mtk: add description of dup3()
 .\"
-.TH DUP 2 2010-09-10 "Linux" "Linux Programmer's Manual"
+.TH DUP 2 2012-02-14 "Linux" "Linux Programmer's Manual"
 .SH NAME
 dup, dup2, dup3 \- duplicate a file descriptor
 .SH SYNOPSIS
@@ -44,6 +44,7 @@ dup, dup2, dup3 \- duplicate a file descriptor
 .BI "int dup2(int " oldfd ", int " newfd );
 .sp
 .BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"
+.BR "#include <fcntl.h>" "              /* Obtain O_* constant definitions */
 .B #include <unistd.h>
 .sp
 .BI "int dup3(int " oldfd ", int " newfd ", int " flags );