diff --git a/doc/plugins/write.mdwn b/doc/plugins/write.mdwn
index 508dd83dc..606031cf2 100644
--- a/doc/plugins/write.mdwn
+++ b/doc/plugins/write.mdwn
@@ -361,10 +361,11 @@ next time ikiwiki is run. The hash holds per-page state, so to set a value,
 use `%pagestate{$page}{$id}{$key}=$value`, and to retrieve the value,
 use `%pagestate{$page}{$id}{$key}`.
 
-`$key` can be any string you like, but `$id` must be the same as the "id"
-parameter passed to `hook()` when registering the plugin. This is so
-ikiwiki can know when to delete pagestate for plugins that are no longer
-used.
+The `$value` can be anything that perl's Storable module is capable of
+serializing. `$key` can be any string you like, but `$id` must be the same
+as the "id" parameter passed to `hook()` when registering the plugin. This
+is so ikiwiki can know when to delete pagestate for plugins that are no
+longer used.
 
 When pages are deleted, ikiwiki automatically deletes their pagestate too.