diff --git a/man7/system_data_types.7 b/man7/system_data_types.7
index 9997b6ba8..5795f5c9e 100644
--- a/man7/system_data_types.7
+++ b/man7/system_data_types.7
@@ -92,6 +92,101 @@ See also:
 .\".I siginfo_t
 .\"type in this page.
 .TP
+.I size_t
+.IP
+Include:
+.I <stddef.h>
+or
+.IR <sys/types.h> ;
+or
+.I <aio.h>
+or
+.I <glob.h>
+or
+.I <grp.h>
+or
+.I <iconv.h>
+or
+.I <monetary.h>
+or
+.I <mqueue.h>
+or
+.I <ndbm.h>
+or
+.I <pwd.h>
+or
+.I <regex.h>
+or
+.I <search.h>
+or
+.I <signal.h>
+or
+.I <stdio.h>
+or
+.I <stdlib.h>
+or
+.I <string.h>
+or
+.I <strings.h>
+or
+.I <sys/mman.h>
+or
+.I <sys/msg.h>
+or
+.I <sys/sem.h>
+or
+.I <sys/shm.h>
+or
+.I <sys/socket.h>
+or
+.I <sys/uio.h>
+or
+.I <time.h>
+or
+.I <unistd.h>
+or
+.I <wchar.h>
+or
+.IR <wordexp.h> .
+.IP
+Used for a count of bytes.  It is the result of the
+.I sizeof
+operator.
+According to the C language standard,
+it shall be an unsigned integer type
+capable of storing values in the range [0,
+.BR SIZE_MAX ].
+.IP
+Conforming to: C99 and later; POSIX.1-2001 and later.
+.IP
+Notes:
+.IR <aio.h> ,
+.IR <glob.h> ,
+.IR <grp.h> ,
+.IR <iconv.h> ,
+.IR <mqueue.h> ,
+.IR <pwd.h> ,
+.IR <signal.h>
+and
+.IR <sys/socket.h>
+define
+.I size_t
+since POSIX.1-2008.
+.IP
+See also:
+.BR fread (3),
+.BR fwrite (3),
+.BR memcmp (3),
+.BR memcpy (3),
+.BR memset (3),
+.BR offsetof (3)
+.IP
+See also the
+.I ssize_t
+and
+.I ptrdiff_t
+types in this page.
+.TP
 .I ssize_t
 .IP
 Include:
@@ -127,10 +222,10 @@ See also:
 .BR recv (2),
 .BR send (2),
 .BR write (2)
-.\".IP	FIXME: When size_t is added, uncomment
-.\"See also the
-.\".I size_t
-.\"type in this page.
+.IP
+See also the
+.I size_t
+type in this page.
 .TP
 .I suseconds_t
 .IP