diff --git a/dashboard/src/translation/en.json b/dashboard/src/translation/en.json
index 34d069d1b..4367dc03f 100644
--- a/dashboard/src/translation/en.json
+++ b/dashboard/src/translation/en.json
@@ -244,7 +244,8 @@
             "bindPassword": "Bind Password (optional)",
             "errorSelfSignedCert": "Server is using an invalid or self-signed certificate.",
             "providerOther": "Other",
-            "providerDisabled": "Disabled"
+            "providerDisabled": "Disabled",
+            "disableWarning": "The authentication source of all existing users will be reset to authenticate against the local password database."
         },
         "subscriptionDialog": {
             "title": "Subscription required",
diff --git a/dashboard/src/views/user-settings.html b/dashboard/src/views/user-settings.html
index 9a79dcc8a..ccbbc46b9 100644
--- a/dashboard/src/views/user-settings.html
+++ b/dashboard/src/views/user-settings.html
@@ -13,6 +13,10 @@
           <select class="form-control" id="ldapProvider" ng-model="externalLdap.provider" ng-options="a.value as a.name for a in ldapProvider"></select>
         </div>
 
+        <p class="text-small text-warning" ng-show="externalLdap.provider === 'noop' && externalLdap.currentConfig.provider !== 'noop'">
+          {{ 'users.externalLdap.disableWarning' | tr }}
+        </p>
+
         <div uib-collapse="externalLdap.provider === 'noop'">
           <form name="externalLdapConfigForm" role="form" novalidate ng-submit="externalLdap.submit()" autocomplete="off">
             <fieldset>
diff --git a/src/externalldap.js b/src/externalldap.js
index 775fa335b..d1bdb575c 100644
--- a/src/externalldap.js
+++ b/src/externalldap.js
@@ -81,6 +81,8 @@ async function setConfig(newConfig) {
     if (error) throw error;
 
     await settings.setJson(settings.EXTERNAL_LDAP_KEY, newConfig);
+
+    if (newConfig.provider === 'noop') await users.resetSource(); // otherwise, the owner could be 'ldap' source and lock themselves out
 }
 
 // performs service bind if required
diff --git a/src/users.js b/src/users.js
index b456fe9f5..4265dd51c 100644
--- a/src/users.js
+++ b/src/users.js
@@ -54,6 +54,8 @@ exports = module.exports = {
     getProfileConfig,
     setProfileConfig,
 
+    resetSource,
+
     AP_MAIL: 'mail',
     AP_WEBADMIN: 'webadmin',
 
@@ -972,3 +974,7 @@ async function setProfileConfig(profileConfig) {
         }
     }
 }
+
+async function resetSource() {
+    await database.query('UPDATE users SET source = ?', [ '' ]);
+}