--- a/zgrep.1	2012-09-10 03:20:56.541637782 +0300
+++ b/zgrep.1	2012-09-10 03:18:21.000000000 +0300
@@ -11,7 +11,13 @@ zgrep \- search possibly compressed file
 invokes
 .I grep
 on compressed or gzipped files.
-All options specified are passed directly to
+These
+.I grep
+options will cause
+.I zgrep
+to terminate with an error code:
+.BI (-[drRzZ] | --di* | --exc* | --inc* | --rec* | --nu*) .
+All other options specified are passed directly to
 .IR grep .
 If no file is specified, then the standard input is decompressed
 if necessary and fed to grep.
@@ -23,6 +29,8 @@ If the GREP environment variable is set,
 uses it as the
 .I grep
 program to be invoked.
+.SH EXIT CODE
+2 - An option that is not supported was specified.
 .SH AUTHOR
 Charles Levert (charles@comm.polymtl.ca)
 .SH "SEE ALSO"