diff --git a/http/whiteboard/src/main/java/org/apache/felix/http/whiteboard/internal/manager/HttpContextManager.java b/http/whiteboard/src/main/java/org/apache/felix/http/whiteboard/internal/manager/HttpContextManager.java
index 12445be..634cbea 100644
--- a/http/whiteboard/src/main/java/org/apache/felix/http/whiteboard/internal/manager/HttpContextManager.java
+++ b/http/whiteboard/src/main/java/org/apache/felix/http/whiteboard/internal/manager/HttpContextManager.java
@@ -192,8 +192,9 @@
 
         this.idMap.put(id, holder);
         this.contextMap.put(context, id);
-
-        return holder.getMappings();
+        
+        // return a copy to prevent concurrent modification
+        return new HashSet<AbstractMapping>(holder.getMappings());
     }
 
     public synchronized Collection<AbstractMapping> removeHttpContext(HttpContext context)