diff --git a/src/externalldap.js b/src/externalldap.js
index f6ac36bb8..11c6120e9 100644
--- a/src/externalldap.js
+++ b/src/externalldap.js
@@ -376,7 +376,7 @@ function syncUsers(externalLdapConfig, progressCallback, callback) {
     assert.strictEqual(typeof progressCallback, 'function');
     assert.strictEqual(typeof callback, 'function');
 
-    ldapUserSearch(externalLdapConfig, {}, function (error, ldapUsers) {
+    ldapUserSearch(externalLdapConfig, {}, async function (error, ldapUsers) {
         if (error) return callback(error);
 
         debug(`Found ${ldapUsers.length} users`);
@@ -385,44 +385,38 @@ function syncUsers(externalLdapConfig, progressCallback, callback) {
         let step = 30/(ldapUsers.length+1); // ensure no divide by 0
 
         // we ignore all errors here and just log them for now
-        async.eachSeries(ldapUsers, function (user, iteratorCallback) {
-            user = translateUser(externalLdapConfig, user);
-
-            if (!validUserRequirements(user)) return iteratorCallback();
+        for (let i = 0; i < ldapUsers.length; i++) {
+            let ldapUser = translateUser(externalLdapConfig, ldapUsers[i]);
+            if (!validUserRequirements(ldapUser)) continue;
 
             percent += step;
-            progressCallback({ percent, message: `Syncing... ${user.username}` });
+            progressCallback({ percent, message: `Syncing... ${ldapUser.username}` });
 
-            users.getByUsername(user.username, function (error, result) {
-                if (error && error.reason !== BoxError.NOT_FOUND) return iteratorCallback(error);
+            const [userGetError, user] = await safe(users.getByUsername(ldapUser.username));
+            if (userGetError) {
+                debug('syncUsers: Failed to get user by username', ldapUser, userGetError);
+                break;
+            }
 
-                if (!result) {
-                    debug(`[adding user] username=${user.username} email=${user.email} displayName=${user.displayName}`);
+            if (!user) {
+                debug(`[adding user] username=${ldapUser.username} email=${ldapUser.email} displayName=${ldapUser.displayName}`);
 
-                    users.create(user.username, null /* password */, user.email, user.displayName, { source: 'ldap' }, auditSource.EXTERNAL_LDAP_TASK, function (error) {
-                        if (error) debug('syncUsers: Failed to create user', user, error.message);
-                        iteratorCallback();
-                    });
-                } else if (result.source !== 'ldap') {
-                    debug(`[conflicting user] username=${user.username} email=${user.email} displayName=${user.displayName}`);
+                const [userAddError] = await safe(users.add(ldapUser.email, { username: ldapUser.username, password: null, displayName: ldapUser.displayName, source: 'ldap' }, auditSource.EXTERNAL_LDAP_TASK));
+                if (userAddError) debug('syncUsers: Failed to create user', ldapUser, userAddError.message);
+            } else if (user.source !== 'ldap') {
+                debug(`[conflicting user] username=${ldapUser.username} email=${ldapUser.email} displayName=${ldapUser.displayName}`);
+            } else if (user.email !== ldapUser.email || user.displayName !== ldapUser.displayName) {
+                debug(`[updating user] username=${ldapUser.username} email=${ldapUser.email} displayName=${ldapUser.displayName}`);
 
-                    iteratorCallback();
-                } else if (result.email !== user.email || result.displayName !== user.displayName) {
-                    debug(`[updating user] username=${user.username} email=${user.email} displayName=${user.displayName}`);
+                const [userUpdateError] = await safe(users.update(user, { email: ldapUser.email, fallbackEmail: ldapUser.email, displayName: ldapUser.displayName }, auditSource.EXTERNAL_LDAP_TASK));
+                if (userUpdateError) debug('Failed to update user', ldapUser, userUpdateError);
+            } else {
+                // user known and up-to-date
+                debug(`[up-to-date user] username=${ldapUser.username} email=${ldapUser.email} displayName=${ldapUser.displayName}`);
+            }
+        }
 
-                    users.update(result, { email: user.email, fallbackEmail: user.email, displayName: user.displayName }, auditSource.EXTERNAL_LDAP_TASK, function (error) {
-                        if (error) debug('Failed to update user', user, error);
-
-                        iteratorCallback();
-                    });
-                } else {
-                    // user known and up-to-date
-                    debug(`[up-to-date user] username=${user.username} email=${user.email} displayName=${user.displayName}`);
-
-                    iteratorCallback();
-                }
-            });
-        }, callback);
+        callback();
     });
 }