diff --git a/README.md b/README.md
index 9a6eea1..a5c8d94 100644
--- a/README.md
+++ b/README.md
@@ -158,7 +158,7 @@ virtual machine.
 
 ```shell
 export TZ=UTC
-openssl x509 -key class3.key.pem -x509toreq -in class3.crt.pem -out class3.csr.pem \
+openssl x509 -signkey class3.key.pem -x509toreq -in class3.crt.pem -out class3.csr.pem \
   2>&1 | tee -a class3-signing-$(date +%Y%m%d).log
 ```