diff --git a/key.ui/src/main/java/de/uka/ilkd/key/ui/MediatorProofControl.java b/key.ui/src/main/java/de/uka/ilkd/key/ui/MediatorProofControl.java
index 887fc4d6ecc..eb7625c1142 100644
--- a/key.ui/src/main/java/de/uka/ilkd/key/ui/MediatorProofControl.java
+++ b/key.ui/src/main/java/de/uka/ilkd/key/ui/MediatorProofControl.java
@@ -171,6 +171,7 @@ private class AutoModeWorker extends SwingWorker<ApplyStrategyInfo, Object> {
         private final ImmutableList<Goal> goals;
         private final ApplyStrategy applyStrategy;
         private ApplyStrategyInfo info;
+        private final ReentrantLock lock;
         private final Condition ready;
 
         public AutoModeWorker(final Proof proof, final ImmutableList<Goal> goals,
@@ -189,7 +190,8 @@ public AutoModeWorker(final Proof proof, final ImmutableList<Goal> goals,
                 applyStrategy.addProverTaskObserver(ui.getMediator().getAutoSaver());
             }
 
-            ready = new ReentrantLock().newCondition();
+            lock = new ReentrantLock();
+            ready = lock.newCondition();
         }
 
         @Override
@@ -209,7 +211,11 @@ protected void done() {
                     applyStrategy.clear();
                 }
                 ui.getMediator().finishAutoMode(proof, true, true, null);
+
+                lock.lock();
                 ready.signalAll();
+                lock.unlock();
+
                 emitInteractiveAutoMode(initialGoals, proof, info);
 
                 if (info.getException() != null) {