diff --git a/pom.xml b/pom.xml
index 2db4bc6b..abfadc09 100644
--- a/pom.xml
+++ b/pom.xml
@@ -31,6 +31,16 @@
 				<enabled>true</enabled>
 			</snapshots>
 		</repository>
+		<repository>
+			<id>jklm.releases</id>
+			<url>http://mvn.jkeylockmanager.de</url>
+			<releases>
+				<enabled>true</enabled>
+			</releases>
+			<snapshots>
+				<enabled>false</enabled>
+			</snapshots>
+		</repository>
 	</repositories>
 
 	<build>
@@ -234,6 +244,11 @@
 			<artifactId>joda-time</artifactId>
 			<version>2.2</version>
 		</dependency>
+		<dependency>
+			<groupId>de.jkeylockmanager</groupId>
+			<artifactId>jkeylockmanager</artifactId>
+			<version>1.0.0</version>
+		</dependency>
 
 		<dependency>
 			<groupId>net.java.dev.rome</groupId>
diff --git a/src/main/java/com/commafeed/backend/feeds/FeedRefreshUpdater.java b/src/main/java/com/commafeed/backend/feeds/FeedRefreshUpdater.java
index b93bddb4..7054e52e 100644
--- a/src/main/java/com/commafeed/backend/feeds/FeedRefreshUpdater.java
+++ b/src/main/java/com/commafeed/backend/feeds/FeedRefreshUpdater.java
@@ -14,7 +14,6 @@ import javax.inject.Singleton;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import com.commafeed.backend.LockMap;
 import com.commafeed.backend.dao.FeedDAO;
 import com.commafeed.backend.dao.FeedSubscriptionDAO;
 import com.commafeed.backend.model.ApplicationSettings;
@@ -26,13 +25,17 @@ import com.commafeed.backend.pubsubhubbub.SubscriptionHandler;
 import com.commafeed.backend.services.ApplicationSettingsService;
 import com.commafeed.backend.services.FeedUpdateService;
 
+import de.jkeylockmanager.manager.KeyLockManager;
+import de.jkeylockmanager.manager.KeyLockManagers;
+import de.jkeylockmanager.manager.LockCallback;
+
 @Singleton
 public class FeedRefreshUpdater {
 
 	protected static Logger log = LoggerFactory
 			.getLogger(FeedRefreshUpdater.class);
 
-	private static LockMap<String> lockMap = new LockMap<String>();
+	private static final KeyLockManager lockManager = KeyLockManagers.newLock();
 
 	@Inject
 	FeedUpdateService feedUpdateService;
@@ -107,11 +110,14 @@ public class FeedRefreshUpdater {
 
 	}
 
-	private void updateEntry(Feed feed, FeedEntry entry,
-			List<FeedSubscription> subscriptions) {
-		synchronized (lockMap.get(entry.getGuid())) {
-			feedUpdateService.updateEntry(feed, entry, subscriptions);
-		}
+	private void updateEntry(final Feed feed, final FeedEntry entry,
+			final List<FeedSubscription> subscriptions) {
+		lockManager.executeLocked(entry.getGuid(), new LockCallback() {
+			@Override
+			public void doInLock() throws Exception {
+				feedUpdateService.updateEntry(feed, entry, subscriptions);
+			}
+		});
 	}
 
 	private void handlePubSub(final Feed feed) {
diff --git a/src/main/java/com/commafeed/backend/services/UserService.java b/src/main/java/com/commafeed/backend/services/UserService.java
index 56f32ede..502e7771 100644
--- a/src/main/java/com/commafeed/backend/services/UserService.java
+++ b/src/main/java/com/commafeed/backend/services/UserService.java
@@ -46,8 +46,9 @@ public class UserService {
 	PasswordEncryptionService encryptionService;
 
 	public User login(String name, String password) {
-		Preconditions.checkNotNull(name);
-		Preconditions.checkNotNull(password);
+		if (name == null || password == null) {
+			return null;
+		}
 
 		User user = userDAO.findByName(name);
 		if (user != null && !user.isDisabled()) {