diff --git a/helper/communicator/config.go b/helper/communicator/config.go
index a2e262445..5cb3a4716 100644
--- a/helper/communicator/config.go
+++ b/helper/communicator/config.go
@@ -113,7 +113,8 @@ type SSH struct {
 	// use this option with a key pair already configured in the source AMI,
 	// leave the `ssh_keypair_name` blank. To associate an existing key pair in
 	// AWS with the source instance, set the `ssh_keypair_name` field to the
-	// name of the key pair.
+	// name of the key pair. The environment variable `SSH_AUTH_SOCK` must be
+	// set for this option to work properly.
 	SSHAgentAuth bool `mapstructure:"ssh_agent_auth"`
 	// If true, SSH agent forwarding will be disabled. Defaults to `false`.
 	SSHDisableAgentForwarding bool `mapstructure:"ssh_disable_agent_forwarding"`
diff --git a/website/source/partials/helper/communicator/_SSH-not-required.html.md b/website/source/partials/helper/communicator/_SSH-not-required.html.md
index 0542cae14..629654786 100644
--- a/website/source/partials/helper/communicator/_SSH-not-required.html.md
+++ b/website/source/partials/helper/communicator/_SSH-not-required.html.md
@@ -46,7 +46,8 @@
     use this option with a key pair already configured in the source AMI,
     leave the `ssh_keypair_name` blank. To associate an existing key pair in
     AWS with the source instance, set the `ssh_keypair_name` field to the
-    name of the key pair.
+    name of the key pair. The environment variable `SSH_AUTH_SOCK` must be
+    set for this option to work properly.
     
 -   `ssh_disable_agent_forwarding` (bool) - If true, SSH agent forwarding will be disabled. Defaults to `false`.