diff --git a/core/src/main/scala/spark/deploy/master/MasterWebUI.scala b/core/src/main/scala/spark/deploy/master/MasterWebUI.scala
index dfec1d1dc552eed9abac8aaeb622dc0d43e6d4d1..a96b55d6f32ca2f9773f5f74a94641afb689f1f8 100644
--- a/core/src/main/scala/spark/deploy/master/MasterWebUI.scala
+++ b/core/src/main/scala/spark/deploy/master/MasterWebUI.scala
@@ -22,13 +22,13 @@ class MasterWebUI(val actorSystem: ActorSystem, master: ActorRef) extends Direct
   
   val handler = {
     get {
-      (path("") & parameters('json ?)) {
-        case Some(js) =>
+      (path("") & parameters('format ?)) {
+        case Some(js) if js.equalsIgnoreCase("json") =>
           val future = master ? RequestMasterState
           respondWithMediaType(MediaTypes.`application/json`) { ctx =>
             ctx.complete(future.mapTo[MasterState])
           }
-        case None =>
+        case _ =>
           completeWith {
             val future = master ? RequestMasterState
             future.map {
diff --git a/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala b/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala
index a168f54ca03dfc29b19c5901c568bc71c77931e4..84b6c16bd6279694bdb389f08383139608d98786 100644
--- a/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala
+++ b/core/src/main/scala/spark/deploy/worker/WorkerWebUI.scala
@@ -21,14 +21,14 @@ class WorkerWebUI(val actorSystem: ActorSystem, worker: ActorRef) extends Direct
   
   val handler = {
     get {
-      (path("") & parameters('json ?)) {
-        case Some(js) => {
+      (path("") & parameters('format ?)) {
+        case Some(js) if js.equalsIgnoreCase("json") => {
           val future = worker ? RequestWorkerState
           respondWithMediaType(MediaTypes.`application/json`) { ctx =>
             ctx.complete(future.mapTo[WorkerState])
           }
         }
-        case None =>
+        case _ =>
           completeWith{
             val future = worker ? RequestWorkerState
             future.map { workerState =>