diff --git a/bundles/org.openhab.io.hueemulation/src/test/java/org/openhab/io/hueemulation/internal/rest/mocks/DummyMetadataRegistry.java b/bundles/org.openhab.io.hueemulation/src/test/java/org/openhab/io/hueemulation/internal/rest/mocks/DummyMetadataRegistry.java
index 04606f104..3c17b7b68 100644
--- a/bundles/org.openhab.io.hueemulation/src/test/java/org/openhab/io/hueemulation/internal/rest/mocks/DummyMetadataRegistry.java
+++ b/bundles/org.openhab.io.hueemulation/src/test/java/org/openhab/io/hueemulation/internal/rest/mocks/DummyMetadataRegistry.java
@@ -17,6 +17,7 @@ import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
@@ -95,6 +96,12 @@ public class DummyMetadataRegistry implements MetadataRegistry {
         return false;
     }
 
+    @Override
+    public Collection<String> getAllNamespaces(String itemname) {
+        return stream().map(Metadata::getUID).filter(key -> key.getItemName().equals(itemname))
+                .map(MetadataKey::getNamespace).collect(Collectors.toSet());
+    }
+
     @Override
     public void removeItemMetadata(String name) {
     }