diff --git a/src/externalldap.js b/src/externalldap.js
index 3e09e51e6..7dc26e94c 100644
--- a/src/externalldap.js
+++ b/src/externalldap.js
@@ -83,8 +83,8 @@ function testConfig(config, callback) {
             if (error) return callback(new BoxError(BoxError.EXTERNAL_ERROR, error));
 
             result.on('searchEntry', function (/* entry */) {});
-            result.on('error', function (error) { callback(new BoxError(BoxError.BAD_FIELD, `Unable to search directory: ${error.message}`)); });
-            result.on('end', function (/* result */) { callback(); });
+            result.on('error', function (error) { client.unbind(); callback(new BoxError(BoxError.BAD_FIELD, `Unable to search directory: ${error.message}`)); });
+            result.on('end', function (/* result */) { client.unbind(); callback(); });
         });
     });
 }
@@ -179,6 +179,11 @@ function sync(progressCallback, callback) {
 
                         const username = user[externalLdapConfig.usernameField];
 
+                        if (!username) {
+                            debug(`[empty username] username=${username} email=${user.mail} cn=${user.cn} usernameField=${externalLdapConfig.usernameField}`);
+                            return iteratorCallback();
+                        }
+
                         users.getByUsername(username, function (error, result) {
                             if (error && error.reason !== BoxError.NOT_FOUND) {
                                 debug(`Could not find user with username ${username}: ${error.message}`);
@@ -213,6 +218,7 @@ function sync(progressCallback, callback) {
                         });
                     }, function () {
                         debug('User sync done.');
+                        client.unbind();
                         callback();
                     });
                 });