diff --git a/README.md b/README.md
index 08cb084..5fa6344 100644
--- a/README.md
+++ b/README.md
@@ -48,7 +48,7 @@ CN=rotuer openssl req -config openssl.cnf -newkey rsa:2048 -nodes -keyout client
 # build and start the server
 nix-build && result/bin/certifix  --challenge-password psk  --ca-certificate ca.crt --ca-private-key --server-certificate server.crt --server-private-key server.key localhost:19613
 # send it
-curl -v -H 'content-type: application/x-pem-file' --data-binary @client.csr  https://localhost:19613/sign
+curl --cacert ca.crt   -v -H 'content-type: application/x-pem-file' --data-binary @client.csr  https://localhost:19613/sign
 ```
 
 ## Reasons this is not secure