diff --git a/man8/thin_trim.8 b/man8/thin_trim.8
index 050135a..6a02e79 100644
--- a/man8/thin_trim.8
+++ b/man8/thin_trim.8
@@ -5,6 +5,9 @@ thin_trim \- Issue discard requests for free pool space (offline tool).
 .SH SYNOPSIS
 .B thin_trim
 .RB [ options ]
+.B --metadata-dev
+.I {device|file}
+.B --data-dev
 .I {device|file}
 
 .SH DESCRIPTION