diff --git a/modules/installation-mirror-repository.adoc b/modules/installation-mirror-repository.adoc
index b0cfee82482b..7d5c090d3764 100644
--- a/modules/installation-mirror-repository.adoc
+++ b/modules/installation-mirror-repository.adoc
@@ -16,6 +16,13 @@ can access the certificate and credentials that you configured.
 * You downloaded the pull secret from the
 link:https://cloud.redhat.com/openshift/install/pull-secret[Pull Secret] page on the {cloud-redhat-com} site and modified it to include authentication to your mirror repository.
 
+* If you use self-signed certificates that do not set a Subject Alternative Name, you must precede the `oc` commands in this procedure with `GODEBUG=x509ignoreCN=0`. If you do not set this variable, the `oc` commands will fail with the following error:
++
+[source,terminal]
+----
+x509: certificate relies on legacy Common Name field, use SANs or temporarily enable Common Name matching with GODEBUG=x509ignoreCN=0
+----
+
 .Procedure
 
 Complete the following steps on the mirror host: