diff --git a/docs/manpages/ndnsec-export.rst b/docs/manpages/ndnsec-export.rst
index fb3c41f..dc94939 100644
--- a/docs/manpages/ndnsec-export.rst
+++ b/docs/manpages/ndnsec-export.rst
@@ -24,6 +24,12 @@
 ``-o output``
   Write to an output file instead of the standard output.
 
+``-P passphrase``
+  Passphrase to use for the export. If not specified (or specified an empty passphrase), the
+  user is interactively asked to input the passphrase on the terminal. Note that specifying
+  passphrase via -P is insecure, as it can potentially end up in shell history, be visible in
+  ps output, etc.
+
 ``identity``
   The identity name.