diff --git a/dz3-model/src/main/java/net/sf/dz3/device/model/impl/AbstractDamperController.java b/dz3-model/src/main/java/net/sf/dz3/device/model/impl/AbstractDamperController.java
index f8303d899..8863062aa 100644
--- a/dz3-model/src/main/java/net/sf/dz3/device/model/impl/AbstractDamperController.java
+++ b/dz3-model/src/main/java/net/sf/dz3/device/model/impl/AbstractDamperController.java
@@ -130,7 +130,10 @@ public synchronized void remove(Thermostat ts) {
         ts2damper.remove(ts);
     }
 
-    public synchronized void stateChanged(Thermostat source, ThermostatSignal signal) {
+    /**
+     * {@inheritDoc}
+     */
+    public synchronized Future<TransitionStatus> stateChanged(Thermostat source, ThermostatSignal signal) {
 
         ThreadContext.push("signalChanged");
 
@@ -146,12 +149,11 @@ public synchronized void stateChanged(Thermostat source, ThermostatSignal signal
             logger.info("Demand: " + source.getName() + "=" + signal.demand.sample);
             logger.info("ts2signal.size()=" + ts2signal.size());
             
-            sync();
+            return sync();
 
         } finally {
             ThreadContext.pop();
         }
-
     }
 
     public synchronized void consume(DataSample<UnitSignal> signal) {
@@ -206,7 +208,7 @@ public synchronized void consume(DataSample<UnitSignal> signal) {
         }
     }
     
-    private void park(boolean async) {
+    private Future<TransitionStatus> park(boolean async) {
 
         ThreadContext.push("park");
         
@@ -224,10 +226,12 @@ private void park(boolean async) {
                 damperMap.put(d, d.getParkPosition());
             }
 
-            shuffle(damperMap, async);
+            Future<TransitionStatus> done = shuffle(damperMap, async);
 
             logger.info("parked");
 
+            return done;
+
         } finally {
             ThreadContext.pop();
         }
@@ -310,7 +314,7 @@ public synchronized String[] getDamperMap() {
     /**
      * Recalculate the damper state according to [possibly] changed internal state.
      */
-    protected final void sync() {
+    protected final Future<TransitionStatus> sync() {
         
         // VT: NOTE: This assumes compute() is stateless, ideally, it should stay that way.
         // If there is ever a need to make it stateful, compute() should be called outside
@@ -318,11 +322,11 @@ protected final void sync() {
         
         if (this.hvacSignal != null && this.hvacSignal.sample.running) {
         
-            shuffle(compute(), true);
+            return shuffle(compute(), true);
             
         } else {
             
-            park(true);
+            return park(true);
         }
     }
 
diff --git a/dz3-model/src/test/java/net/sf/dz3/device/model/impl/BalancingDamperControllerTest.java b/dz3-model/src/test/java/net/sf/dz3/device/model/impl/BalancingDamperControllerTest.java
index 31eb02b8d..a56e97ed6 100644
--- a/dz3-model/src/test/java/net/sf/dz3/device/model/impl/BalancingDamperControllerTest.java
+++ b/dz3-model/src/test/java/net/sf/dz3/device/model/impl/BalancingDamperControllerTest.java
@@ -2,6 +2,7 @@
 
 import java.io.IOException;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Future;
 
 import org.apache.logging.log4j.LogManager;
@@ -59,7 +60,7 @@ public void testBoundaries() {
     /**
      * Make sure that zero demand from all thermostats doesn't cause NaN sent to dampers.
      */
-    public void testNaN() {
+    public void testNaN() throws InterruptedException, ExecutionException {
         
         ThreadContext.push("testNaN");
         
@@ -76,7 +77,11 @@ public void testNaN() {
             // No calculations are performed unless the HVAC unit signal is present
             damperController.consume(new DataSample<UnitSignal>("unit1", "unit1", new UnitSignal(1.0, true, 0), null));
 
-            damperController.stateChanged(ts1, new ThermostatSignal(true, false, true, true, new DataSample<Double>("ts1", "ts1", -50.0, null)));
+            Future<TransitionStatus> done = damperController.stateChanged(ts1, new ThermostatSignal(true, false, true, true, new DataSample<Double>("ts1", "ts1", -50.0, null)));
+
+            TransitionStatus status = done.get();
+
+            assertTrue(status.isOK());
 
             logger.debug("about to assert");