diff --git a/Exareme-Docker/src/exareme/exareme-master/src/main/java/madgik/exareme/master/engine/scheduler/AdpDBQueryScheduler.java b/Exareme-Docker/src/exareme/exareme-master/src/main/java/madgik/exareme/master/engine/scheduler/AdpDBQueryScheduler.java
index fd785d00c..15036ca9e 100644
--- a/Exareme-Docker/src/exareme/exareme-master/src/main/java/madgik/exareme/master/engine/scheduler/AdpDBQueryScheduler.java
+++ b/Exareme-Docker/src/exareme/exareme-master/src/main/java/madgik/exareme/master/engine/scheduler/AdpDBQueryScheduler.java
@@ -29,6 +29,7 @@
 import madgik.exareme.utils.eventProcessor.EventProcessor;
 
 import java.rmi.RemoteException;
+import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
diff --git a/Exareme-Docker/src/exareme/exareme-worker/src/main/java/madgik/exareme/worker/art/executionEngine/dynamicExecutionEngine/DynamicPlanManager.java b/Exareme-Docker/src/exareme/exareme-worker/src/main/java/madgik/exareme/worker/art/executionEngine/dynamicExecutionEngine/DynamicPlanManager.java
index bf5ca2615..fd2bf4c36 100644
--- a/Exareme-Docker/src/exareme/exareme-worker/src/main/java/madgik/exareme/worker/art/executionEngine/dynamicExecutionEngine/DynamicPlanManager.java
+++ b/Exareme-Docker/src/exareme/exareme-worker/src/main/java/madgik/exareme/worker/art/executionEngine/dynamicExecutionEngine/DynamicPlanManager.java
@@ -25,6 +25,8 @@
 import java.util.Map;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * @author herald
@@ -34,6 +36,7 @@ public class DynamicPlanManager implements PlanSessionManagerInterface {
     private final HashMap<PlanSessionID, PlanSessionReportID> elasticTreeSessions = new HashMap<>();
     private EventProcessor eventProcessor = null;
     private long sessionCount = 0;
+    ReentrantLock sessionCountLock = new ReentrantLock();
     private long containerSessionCount = 0;
     /* ROOT sessions */
     private Map<PlanSessionID, PlanEventScheduler> schedulerMap = null;
@@ -71,11 +74,13 @@ public void setExecutionEngine(ExecutionEngine executionEngine) {
 
     @Override
     public void createGlobalScheduler() throws RemoteException {
+        sessionCountLock.lock();
         PlanSessionID sessionID = new PlanSessionID(sessionCount);
         PlanSessionReportID reportID = new PlanSessionReportID(sessionCount);
-        reportID.reportManagerProxy = executionEngine.getPlanSessionReportManagerProxy(reportID);
         sessionCount++;
+        sessionCountLock.unlock();
 
+        reportID.reportManagerProxy = executionEngine.getPlanSessionReportManagerProxy(reportID);
         PlanEventScheduler eventScheduler =
                 new PlanEventScheduler(sessionID, reportID, eventProcessor, this, resourceManager,
                         registryProxy);
@@ -86,12 +91,13 @@ public void createGlobalScheduler() throws RemoteException {
 
     @Override
     public PlanSessionID createNewSession() throws RemoteException {
-        // TODO Is this thread safe?
+        sessionCountLock.lock();
         PlanSessionID sessionID = new PlanSessionID(sessionCount);
         PlanSessionReportID reportID = new PlanSessionReportID(sessionCount);
-        reportID.reportManagerProxy = executionEngine.getPlanSessionReportManagerProxy(reportID);
         sessionCount++;
+        sessionCountLock.unlock();
 
+        reportID.reportManagerProxy = executionEngine.getPlanSessionReportManagerProxy(reportID);
         PlanEventScheduler eventScheduler =
                 new PlanEventScheduler(sessionID, reportID, eventProcessor, this, resourceManager,
                         registryProxy);