diff --git a/dashboard/src/views/emails.js b/dashboard/src/views/emails.js
index 5e54ebd09..96f6a55d9 100644
--- a/dashboard/src/views/emails.js
+++ b/dashboard/src/views/emails.js
@@ -438,8 +438,9 @@ angular.module('Application').controller('EmailsController', ['$scope', '$locati
                         if (error) return console.error('Failed to fetch usage for domain', domain.domain, error);
 
                         domain.usage = 0;
-                        // quotaValue can be missing for deleted mailboxes that are on disk but removed from dovecot/ldap itself
-                        Object.keys(usage).forEach(function (m) { domain.usage += (usage[m].quotaValue || usage[m].diskSize); });
+                        // we used to use quotaValue here but it's quite different wrt diskSize. so choose diskSize consistently
+                        // also, quotaValue can be missing for deleted mailboxes that are on disk but removed from dovecot/ldap itself
+                        Object.keys(usage).forEach(function (m) { domain.usage += usage[m].diskSize; });
                     });
                 });
             });