diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index e63bcdb..a80c4c8 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -4201,6 +4201,8 @@
 'key'			string	(default "")
 			local to buffer
 			{not in Vi}
+			{only available when compiled with the |+cryptv|
+			feature}
 	The key that is used for encrypting and decrypting the current buffer.
 	See |encryption| and 'cryptmethod'.
 	Careful: Do not set the key value by hand, someone might see the typed