diff --git a/README.md b/README.md
index e6a02fa..7b63d14 100644
--- a/README.md
+++ b/README.md
@@ -39,3 +39,6 @@ of Timeout and if no activity is seen even after that the connection is closed
 GW_KEEPALIVE_PERMIT_WITHOUT_STREAM=Bool - if true, client sends keepalive pings even with no active RPCs.
 If false, when there are no active RPCs, Time and Timeout will be ignored and no keepalive pings will be sent.
 ```
+
+### WARNING
+`generated` value for `GW_KEY` or `--key` is deprecated, you should use pre-generated keys.
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