diff --git a/man7/unix.7 b/man7/unix.7
index 4fbe28ae6..29a54958c 100644
--- a/man7/unix.7
+++ b/man7/unix.7
@@ -12,7 +12,7 @@
 .\"     address that can appear in the sockaddr_un structure: pathname,
 .\"     unnamed, and abstract.
 .\"
-.TH UNIX  7 2008-08-08 "Linux" "Linux Programmer's Manual"
+.TH UNIX  7 2008-09-01 "Linux" "Linux Programmer's Manual"
 .SH NAME
 unix, AF_UNIX, AF_LOCAL \- Sockets for local
 interprocess communication
@@ -211,6 +211,9 @@ This can be used for authentication.
 The credentials are passed as a
 .I struct ucred
 ancillary message.
+Thus structure is defined in
+.I <sys/socket.h>
+as follows:
 
 .in +4n
 .nf
@@ -222,6 +225,11 @@ struct ucred {
 .fi
 .in
 
+Since glibc 2.8, the
+.B __GNU_SOURCE
+feature test macro must be defined in order to obtain the definition
+of this structure.
+
 The credentials which the sender specifies are checked by the kernel.
 A process with effective user ID 0 is allowed to specify values that do
 not match its own.