diff --git a/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala b/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala
index 555c26aad1811..e5036fbc6d626 100644
--- a/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala
+++ b/external/mqtt/src/main/scala/org/apache/spark/streaming/mqtt/MQTTTestUtils.scala
@@ -111,7 +111,7 @@ private class MQTTTestUtils extends Logging {
   /**
    * Block until at least one receiver has started or timeout occurs.
    */
-  def waitForReceiverToStart(ssc: StreamingContext) = {
+  def waitForReceiverToStart(ssc: StreamingContext) : Unit = {
     val latch = new CountDownLatch(1)
     ssc.addStreamingListener(new StreamingListener {
       override def onReceiverStarted(receiverStarted: StreamingListenerReceiverStarted) {
diff --git a/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala b/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala
index 4d352cba96a3a..d406749c9b4f1 100644
--- a/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala
+++ b/external/mqtt/src/test/scala/org/apache/spark/streaming/mqtt/MQTTStreamSuite.scala
@@ -54,8 +54,10 @@ class MQTTStreamSuite extends SparkFunSuite with Eventually with BeforeAndAfterA
     val sparkConf = new SparkConf().setMaster("local[4]").setAppName(this.getClass.getSimpleName)
     ssc = new StreamingContext(sparkConf, Milliseconds(500))
     val sendMessage = "MQTT demo for spark streaming"
-    val receiveStream =
-      MQTTUtils.createStream(ssc, "tcp://" + MQTTTestUtils.brokerUri, topic, StorageLevel.MEMORY_ONLY)
+
+    val receiveStream = MQTTUtils.createStream(ssc, "tcp://" + MQTTTestUtils.brokerUri, topic,
+      StorageLevel.MEMORY_ONLY)
+
     @volatile var receiveMessage: List[String] = List()
     receiveStream.foreachRDD { rdd =>
       if (rdd.collect.length > 0) {