Index: head/usr.sbin/newsyslog/newsyslog.c
===================================================================
--- head/usr.sbin/newsyslog/newsyslog.c
+++ head/usr.sbin/newsyslog/newsyslog.c
@@ -1193,6 +1193,12 @@
 		if (!sscanf(q, "%o", &working->permissions))
 			errx(1, "error in config file; bad permissions:\n%s",
 			    errline);
+		if ((working->permissions & ~DEFFILEMODE) != 0) {
+			warnx("File mode bits 0%o changed to 0%o in line:\n%s",
+			    working->permissions,
+			    working->permissions & DEFFILEMODE, errline);
+			working->permissions &= DEFFILEMODE;
+		}
 
 		q = parse = missing_field(sob(parse + 1), errline);
 		parse = son(parse);
Index: head/usr.sbin/newsyslog/newsyslog.conf.5
===================================================================
--- head/usr.sbin/newsyslog/newsyslog.conf.5
+++ head/usr.sbin/newsyslog/newsyslog.conf.5
@@ -21,7 +21,7 @@
 .\" the suitability of this software for any purpose.  It is
 .\" provided "as is" without express or implied warranty.
 .\"
-.Dd January 15, 2018
+.Dd August 21, 2018
 .Dt NEWSYSLOG.CONF 5
 .Os
 .Sh NAME
@@ -96,6 +96,11 @@
 .Pa /etc/group .
 .It Ar mode
 Specify the file mode of the log file and archives.
+Valid mode bits are
+.Dv 0666 .
+(That is, read and write permissions for the rotated log may be specified for
+the owner, group, and others.)
+All other mode bits are ignored.
 .It Ar count
 Specify the maximum number of archive files which may exist.
 This does not consider the current log file.