diff --git a/li.strolch.service/src/main/java/li/strolch/execution/EventBasedExecutionHandler.java b/li.strolch.service/src/main/java/li/strolch/execution/EventBasedExecutionHandler.java
index 131915b20..550a00cf4 100644
--- a/li.strolch.service/src/main/java/li/strolch/execution/EventBasedExecutionHandler.java
+++ b/li.strolch.service/src/main/java/li/strolch/execution/EventBasedExecutionHandler.java
@@ -45,11 +45,11 @@ public class EventBasedExecutionHandler extends ExecutionHandler {
 	}
 
 	@Override
-	public Collection<Controller> getControllers(String realm) {
+	public List<Controller> getControllers(String realm) {
 		Map<Locator, Controller> controllersByRealm = this.controllers.getMap(realm);
 		if (controllersByRealm == null)
-			return Collections.emptyList();
-		return controllersByRealm.values();
+			return new ArrayList<>();
+		return new ArrayList<>(controllersByRealm.values());
 	}
 
 	@Override
diff --git a/li.strolch.service/src/main/java/li/strolch/execution/ExecutionHandler.java b/li.strolch.service/src/main/java/li/strolch/execution/ExecutionHandler.java
index 178375073..861d547e3 100644
--- a/li.strolch.service/src/main/java/li/strolch/execution/ExecutionHandler.java
+++ b/li.strolch.service/src/main/java/li/strolch/execution/ExecutionHandler.java
@@ -1,6 +1,7 @@
 package li.strolch.execution;
 
 import java.util.Collection;
+import java.util.List;
 import java.util.Set;
 import java.util.concurrent.ExecutorService;
 
@@ -76,7 +77,7 @@ public abstract class ExecutionHandler extends StrolchComponent {
 	 *
 	 * @return the controllers
 	 */
-	public abstract Collection<Controller> getControllers(String realm);
+	public abstract List<Controller> getControllers(String realm);
 
 	/**
 	 * Returns the controller for the given realm and activity, null if it does not exist