diff --git a/man7/system_data_types.7 b/man7/system_data_types.7
index 49ca2d8e1..2d23363bb 100644
--- a/man7/system_data_types.7
+++ b/man7/system_data_types.7
@@ -133,6 +133,27 @@ See also:
 .BR timer_create (2),
 .BR clock_getcpuclockid (3)
 .RE
+.\"------------------------------------- dev_t ------------------------/
+.TP
+.I dev_t
+.RS
+Include:
+.IR <sys/types.h> .
+Alternatively,
+.IR <sys/stat.h> .
+.PP
+Used for device IDs.
+According to POSIX,
+it shall be an integer type.
+.PP
+Conforming to:
+POSIX.1-2001 and later.
+.PP
+See also:
+.BR mknod (2),
+.BR ustat (2),
+.BR makedev (3)
+.RE
 .\"------------------------------------- div_t ------------------------/
 .TP
 .I div_t