diff --git a/src/applications/config/option/PhabricatorAccessLogConfigOptions.php b/src/applications/config/option/PhabricatorAccessLogConfigOptions.php
index 6183f9936f..9ae60825ea 100644
--- a/src/applications/config/option/PhabricatorAccessLogConfigOptions.php
+++ b/src/applications/config/option/PhabricatorAccessLogConfigOptions.php
@@ -35,6 +35,7 @@ final class PhabricatorAccessLogConfigOptions
       'P' => pht('The logged-in user PHID, if one is logged in.'),
       'i' => pht('Request input, in bytes.'),
       'o' => pht('Request output, in bytes.'),
+      'I' => pht('Cluster instance name, if configured.'),
     );
 
     $http_map = $common_map + array(
diff --git a/src/infrastructure/log/PhabricatorAccessLog.php b/src/infrastructure/log/PhabricatorAccessLog.php
index d3d9979aac..2ffa0577a8 100644
--- a/src/infrastructure/log/PhabricatorAccessLog.php
+++ b/src/infrastructure/log/PhabricatorAccessLog.php
@@ -30,6 +30,7 @@ final class PhabricatorAccessLog extends Phobject {
             'h' => php_uname('n'),
             'p' => getmypid(),
             'e' => time(),
+            'I' => PhabricatorEnv::getEnvConfig('cluster.instance'),
           ));
 
       self::$log = $log;
diff --git a/src/infrastructure/log/PhabricatorSSHLog.php b/src/infrastructure/log/PhabricatorSSHLog.php
index 9f9f75b41b..de4c270f72 100644
--- a/src/infrastructure/log/PhabricatorSSHLog.php
+++ b/src/infrastructure/log/PhabricatorSSHLog.php
@@ -20,6 +20,7 @@ final class PhabricatorSSHLog extends Phobject {
         'h' => php_uname('n'),
         'p' => getmypid(),
         'e' => time(),
+        'I' => PhabricatorEnv::getEnvConfig('cluster.instance'),
       );
 
       $sudo_user = PhabricatorEnv::getEnvConfig('phd.user');