diff --git a/parfait-core/src/main/java/com/custardsource/parfait/MonitorableRegistry.java b/parfait-core/src/main/java/com/custardsource/parfait/MonitorableRegistry.java
index <HASH>..<HASH> 100644
--- a/parfait-core/src/main/java/com/custardsource/parfait/MonitorableRegistry.java
+++ b/parfait-core/src/main/java/com/custardsource/parfait/MonitorableRegistry.java
@@ -8,6 +8,7 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;

 

 import com.google.common.base.Preconditions;

+import com.google.common.collect.ImmutableList;

 

 /**

  * A collection of Monitorables to be monitored by a given output source (or

@@ -74,10 +75,7 @@ public class MonitorableRegistry {
      *         MonitorableRegistry.

      */

     public synchronized Collection<Monitorable<?>> getMonitorables() {

-        Preconditions.checkState(stateFrozen,

-                "MonitorableRegistry must be frozen before retrieving monitorable list");

-        stateFrozen = true;

-        return Collections.unmodifiableCollection(monitorables.values());

+        return ImmutableList.copyOf(monitorables.values());

     }

 

     /*
Tidyup of MonitorableRegistry preconditions, better concurrent semantics