diff --git a/examples/src/test/scala/examples/ExperimentalAPIExamples.scala b/examples/src/test/scala/examples/ExperimentalAPIExamples.scala
index 5523462f..db8b69f1 100644
--- a/examples/src/test/scala/examples/ExperimentalAPIExamples.scala
+++ b/examples/src/test/scala/examples/ExperimentalAPIExamples.scala
@@ -64,7 +64,7 @@ object ExperimentalAPIExamples {
   @Test def onBackpressureBufferWithCapacityExample2(): Unit = {
     Observable[Int](subscriber => {
       (1 to 200).foreach(subscriber.onNext)
-    }).onBackpressureBuffer(10, println("Overflow")).observeOn(IOScheduler()).subscribe(
+    }).onBackpressureBuffer(10, () => println("Overflow")).observeOn(IOScheduler()).subscribe(
       v => {
         Thread.sleep(10)
         // A slow consumer
diff --git a/examples/src/test/scala/examples/RxScalaDemo.scala b/examples/src/test/scala/examples/RxScalaDemo.scala
index aaf5681c..0efe1eb8 100644
--- a/examples/src/test/scala/examples/RxScalaDemo.scala
+++ b/examples/src/test/scala/examples/RxScalaDemo.scala
@@ -853,7 +853,7 @@ class RxScalaDemo extends JUnitSuite {
   }
 
   @Test def doOnCompletedExample(): Unit = {
-    val o = List("red", "green", "blue").toObservable.doOnCompleted { println("onCompleted") }
+    val o = List("red", "green", "blue").toObservable.doOnCompleted(() => println("onCompleted"))
     o.subscribe(v => println(v), e => e.printStackTrace)
     // red
     // green
@@ -862,7 +862,7 @@ class RxScalaDemo extends JUnitSuite {
   }
 
   @Test def doOnSubscribeExample(): Unit = {
-    val o = List("red", "green", "blue").toObservable.doOnSubscribe { println("subscribed") }
+    val o = List("red", "green", "blue").toObservable.doOnSubscribe(() => println("subscribed"))
     o.subscribe(v => println(v), e => e.printStackTrace, () => println("onCompleted"))
     // subscribed
     // red
@@ -872,7 +872,7 @@ class RxScalaDemo extends JUnitSuite {
   }
 
   @Test def doOnTerminateExample(): Unit = {
-    val o = List("red", "green", "blue").toObservable.doOnTerminate { println("terminate") }
+    val o = List("red", "green", "blue").toObservable.doOnTerminate(() => println("terminate"))
     o.subscribe(v => println(v), e => e.printStackTrace, () => println("onCompleted"))
     // red
     // green
@@ -882,7 +882,7 @@ class RxScalaDemo extends JUnitSuite {
   }
 
   @Test def doOnUnsubscribeExample(): Unit = {
-    val o = List("red", "green", "blue").toObservable.doOnUnsubscribe { println("unsubscribed") }
+    val o = List("red", "green", "blue").toObservable.doOnUnsubscribe(() => println("unsubscribed"))
     o.subscribe(v => println(v), e => e.printStackTrace, () => println("onCompleted"))
     // red
     // green
@@ -892,7 +892,7 @@ class RxScalaDemo extends JUnitSuite {
   }
 
   @Test def doAfterTerminateExample(): Unit = {
-    val o = List("red", "green", "blue").toObservable.doAfterTerminate { println("finally") }
+    val o = List("red", "green", "blue").toObservable.doAfterTerminate(() => println("finally"))
     o.subscribe(v => println(v), e => e.printStackTrace, () => println("onCompleted"))
     // red
     // green
@@ -1545,7 +1545,7 @@ class RxScalaDemo extends JUnitSuite {
       Observable.interval(100 millis)
         .map(l => s"o$n emit $l")
         .take(3)
-        .doOnSubscribe(println(s"subscribe to o$n"))
+        .doOnSubscribe(() => println(s"subscribe to o$n"))
     }.switch.take(5).subscribe(println(_))
   }
 
@@ -1558,7 +1558,7 @@ class RxScalaDemo extends JUnitSuite {
         Observable.interval(100 millis)
           .map(l => s"o$n emit $l")
           .take(3)
-          .doOnSubscribe(println(s"subscribe to o$n"))
+          .doOnSubscribe(() => println(s"subscribe to o$n"))
       }
     }.switch.subscribe(println(_), _.printStackTrace())
 
@@ -1572,7 +1572,7 @@ class RxScalaDemo extends JUnitSuite {
         Observable.interval(100 millis)
           .map(l => s"o$n emit $l")
           .take(3)
-          .doOnSubscribe(println(s"subscribe to o$n"))
+          .doOnSubscribe(() => println(s"subscribe to o$n"))
       }
     }.delayError.switch.subscribe(println(_), _.printStackTrace())
   }
@@ -1593,7 +1593,7 @@ class RxScalaDemo extends JUnitSuite {
         Observable.interval(100 millis)
           .map(l => s"o$n emit $l")
           .take(3)
-          .doOnSubscribe(println(s"subscribe to o$n"))
+          .doOnSubscribe(() => println(s"subscribe to o$n"))
       }
     }.subscribe(println(_), _.printStackTrace())
 
@@ -1607,7 +1607,7 @@ class RxScalaDemo extends JUnitSuite {
         Observable.interval(100 millis)
           .map(l => s"o$n emit $l")
           .take(3)
-          .doOnSubscribe(println(s"subscribe to o$n"))
+          .doOnSubscribe(() => println(s"subscribe to o$n"))
       }
     }.subscribe(println(_), _.printStackTrace())
   }
@@ -1778,56 +1778,56 @@ class RxScalaDemo extends JUnitSuite {
   }
 
   @Test def concatEagerExample(): Unit = {
-    val o1 = Observable.interval(100 millis).take(3).map(l => s"o1 emit $l").doOnSubscribe(println("subscribe to o1"))
-    val o2 = Observable.interval(100 millis).take(3).map(l => s"o2 emit $l").doOnSubscribe(println("subscribe to o2"))
+    val o1 = Observable.interval(100 millis).take(3).map(l => s"o1 emit $l").doOnSubscribe(() => println("subscribe to o1"))
+    val o2 = Observable.interval(100 millis).take(3).map(l => s"o2 emit $l").doOnSubscribe(() => println("subscribe to o2"))
     o1.concatEager(o2).subscribe(println(_))
   }
 
   @Test def concatEagerExample2(): Unit = {
     (0 until 10).map { i =>
-      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(println(s"subscribe to o$i"))
+      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(() => println(s"subscribe to o$i"))
     }.toObservable.concatEager.subscribe(println(_))
   }
 
   @Test def concatEagerExample3(): Unit = {
     (0 until 10).map { i =>
-      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(println(s"subscribe to o$i"))
+      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(() => println(s"subscribe to o$i"))
     }.toObservable.concatEager(capacityHint = 3).subscribe(println(_))
   }
 
   @Test def concatMapEagerExample(): Unit = {
     (0 until 10).toObservable.concatMapEager { i =>
-      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(println(s"subscribe to o$i"))
+      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(() => println(s"subscribe to o$i"))
     }.subscribe(println(_))
   }
 
   @Test def concatMapEagerExample2(): Unit = {
     (0 until 10).toObservable.concatMapEager(capacityHint = 10, i => {
-      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(println(s"subscribe to o$i"))
+      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(() => println(s"subscribe to o$i"))
     }).subscribe(println(_))
   }
 
   @Test def concatMapEagerExample3(): Unit = {
     (0 until 10).toObservable.concatMapEager(capacityHint = 10, maxConcurrent = 3, i => {
-      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(println(s"subscribe to o$i"))
+      Observable.interval(100 millis).take(3).map(l => s"o$i emit $l").doOnSubscribe(() => println(s"subscribe to o$i"))
     }).subscribe(println(_))
   }
 
   @Test def flattenDelayErrorExample() {
     val o1 = Observable.just(1).delay(200 millis).
-      flatMap(i => Observable.error(new RuntimeException("Oops!"))).doOnSubscribe(println(s"subscribe to o1"))
-    val o2 = Observable.interval(100 millis).map(l => s"o2 emit $l").take(3).doOnSubscribe(println(s"subscribe to o2"))
-    val o3 = Observable.interval(100 millis).map(l => s"o3 emit $l").take(3).doOnSubscribe(println(s"subscribe to o3"))
-    val o4 = Observable.interval(100 millis).map(l => s"o4 emit $l").take(3).doOnSubscribe(println(s"subscribe to o4"))
+      flatMap(i => Observable.error(new RuntimeException("Oops!"))).doOnSubscribe(() => println(s"subscribe to o1"))
+    val o2 = Observable.interval(100 millis).map(l => s"o2 emit $l").take(3).doOnSubscribe(() => println(s"subscribe to o2"))
+    val o3 = Observable.interval(100 millis).map(l => s"o3 emit $l").take(3).doOnSubscribe(() => println(s"subscribe to o3"))
+    val o4 = Observable.interval(100 millis).map(l => s"o4 emit $l").take(3).doOnSubscribe(() => println(s"subscribe to o4"))
     Observable.just(o1, o2, o3, o4).delayError.flatten.subscribe(println(_), _.printStackTrace())
   }
 
   @Test def flattenDelayErrorExample2() {
     val o1 = Observable.just(1).delay(200 millis).
-      flatMap(i => Observable.error(new RuntimeException("Oops!"))).doOnSubscribe(println(s"subscribe to o1"))
-    val o2 = Observable.interval(100 millis).map(l => s"o2 emit $l").take(3).doOnSubscribe(println(s"subscribe to o2"))
-    val o3 = Observable.interval(100 millis).map(l => s"o3 emit $l").take(3).doOnSubscribe(println(s"subscribe to o3"))
-    val o4 = Observable.interval(100 millis).map(l => s"o4 emit $l").take(3).doOnSubscribe(println(s"subscribe to o4"))
+      flatMap(i => Observable.error(new RuntimeException("Oops!"))).doOnSubscribe(() => println(s"subscribe to o1"))
+    val o2 = Observable.interval(100 millis).map(l => s"o2 emit $l").take(3).doOnSubscribe(() => println(s"subscribe to o2"))
+    val o3 = Observable.interval(100 millis).map(l => s"o3 emit $l").take(3).doOnSubscribe(() => println(s"subscribe to o3"))
+    val o4 = Observable.interval(100 millis).map(l => s"o4 emit $l").take(3).doOnSubscribe(() => println(s"subscribe to o4"))
     Observable.just(o1, o2, o3, o4).delayError.flatten(2).subscribe(println(_), _.printStackTrace())
   }
 
@@ -1860,17 +1860,17 @@ class RxScalaDemo extends JUnitSuite {
   }
 
   def autoConnectExample(): Unit = {
-    val o = Observable.just(1, 2, 3).doOnSubscribe {
-      println("Start to emit items")
-    }.publish.autoConnect
+    val o = Observable.just(1, 2, 3)
+      .doOnSubscribe(() => println("Start to emit items"))
+      .publish.autoConnect
     println("1st Observer is subscribing")
     o.subscribe(println(_))
   }
 
   def autoConnectExample2(): Unit = {
-    val o = Observable.just(1, 2, 3).doOnSubscribe {
-      println("Start to emit items")
-    }.publish.autoConnect(3)
+    val o = Observable.just(1, 2, 3)
+      .doOnSubscribe(() => println("Start to emit items"))
+      .publish.autoConnect(3)
     println("1st Observer is subscribing")
     o.subscribe(i => println(s"s1: $i"))
     println("2nd Observer is subscribing")
diff --git a/src/main/scala/rx/lang/scala/Observable.scala b/src/main/scala/rx/lang/scala/Observable.scala
index 82862cea..72f81660 100644
--- a/src/main/scala/rx/lang/scala/Observable.scala
+++ b/src/main/scala/rx/lang/scala/Observable.scala
@@ -1118,8 +1118,8 @@ trait Observable[+T]
    * @return an [[Observable]] that emits the same items as the source [[Observable]], then invokes the `action`
    * @see <a href="http://reactivex.io/documentation/operators/do.html">ReactiveX operators documentation: Do</a>
    */
-  def doAfterTerminate(action: => Unit): Observable[T] = {
-    toScalaObservable[T](asJavaObservable.doAfterTerminate(() => action))
+  def doAfterTerminate(action: () => Unit): Observable[T] = {
+    toScalaObservable[T](asJavaObservable.doAfterTerminate(action))
   }
 
   /**
@@ -3888,8 +3888,8 @@ trait Observable[+T]
    *                    `onCompleted`
    * @return the source Observable with the side-effecting behavior applied
    */
-  def doOnCompleted(onCompleted: => Unit): Observable[T] = {
-    toScalaObservable[T](asJavaObservable.doOnCompleted(() => onCompleted))
+  def doOnCompleted(onCompleted: () => Unit): Observable[T] = {
+    toScalaObservable[T](asJavaObservable.doOnCompleted(onCompleted))
   }
 
   /**
@@ -3949,8 +3949,8 @@ trait Observable[+T]
    * @see <a href="https://github.com/ReactiveX/RxJava/wiki/Observable-Utility-Operators#doonsubscribe">RxJava wiki: doOnSubscribe</a>
    * @since 0.20
    */
-  def doOnSubscribe(onSubscribe: => Unit): Observable[T] = {
-    toScalaObservable[T](asJavaObservable.doOnSubscribe(() => onSubscribe))
+  def doOnSubscribe(onSubscribe: () => Unit): Observable[T] = {
+    toScalaObservable[T](asJavaObservable.doOnSubscribe(onSubscribe))
   }
 
   /**
@@ -3965,8 +3965,8 @@ trait Observable[+T]
    * @see <a href="https://github.com/ReactiveX/RxJava/wiki/Observable-Utility-Operators#wiki-doonterminate">RxJava Wiki: doOnTerminate()</a>
    * @see <a href="http://msdn.microsoft.com/en-us/library/hh229804.aspx">MSDN: Observable.Do</a>
    */
-  def doOnTerminate(onTerminate: => Unit): Observable[T] = {
-    toScalaObservable[T](asJavaObservable.doOnTerminate(() => onTerminate))
+  def doOnTerminate(onTerminate: () => Unit): Observable[T] = {
+    toScalaObservable[T](asJavaObservable.doOnTerminate(onTerminate))
   }
 
   /**
@@ -4003,8 +4003,8 @@ trait Observable[+T]
    * @see <a href="https://github.com/ReactiveX/RxJava/wiki/Observable-Utility-Operators#doonunsubscribe">RxJava wiki: doOnUnsubscribe</a>
    * @since 0.20
    */
-  def doOnUnsubscribe(onUnsubscribe: => Unit): Observable[T] = {
-    toScalaObservable[T](asJavaObservable.doOnUnsubscribe(() => onUnsubscribe))
+  def doOnUnsubscribe(onUnsubscribe: () => Unit): Observable[T] = {
+    toScalaObservable[T](asJavaObservable.doOnUnsubscribe(onUnsubscribe))
   }
 
   /**
@@ -4716,10 +4716,8 @@ trait Observable[+T]
    * @since (if this graduates from Experimental/Beta to supported, replace this parenthetical with the release number)
    */
   @Beta
-  def onBackpressureBuffer(capacity: Long, onOverflow: => Unit): Observable[T] = {
-    asJavaObservable.onBackpressureBuffer(capacity, new Action0 {
-      override def call(): Unit = onOverflow
-    })
+  def onBackpressureBuffer(capacity: Long, onOverflow: () => Unit): Observable[T] = {
+    asJavaObservable.onBackpressureBuffer(capacity, onOverflow)
   }
 
   /**
diff --git a/src/test/scala-2.11/rx/lang/scala/completeness/ObservableCompletenessKit.scala b/src/test/scala-2.11/rx/lang/scala/completeness/ObservableCompletenessKit.scala
index 178d3c25..10bd85a2 100644
--- a/src/test/scala-2.11/rx/lang/scala/completeness/ObservableCompletenessKit.scala
+++ b/src/test/scala-2.11/rx/lang/scala/completeness/ObservableCompletenessKit.scala
@@ -75,14 +75,14 @@ class ObservableCompletenessKit extends CompletenessKit {
     "delaySubscription(Func0[_ <: Observable[U]])" -> "delaySubscription(() => Observable[Any])",
     "delaySubscription(Observable[U])" -> "[use `delaySubscription(() => Observable[Any])`]",
     "dematerialize()" -> "dematerialize(<:<[Observable[T], Observable[Notification[U]]])",
-    "doOnCompleted(Action0)" -> "doOnCompleted(=> Unit)",
+    "doOnCompleted(Action0)" -> "doOnCompleted(() => Unit)",
     "doOnEach(Action1[Notification[_ >: T]])" -> "[use `doOnEach(T => Unit, Throwable => Unit, () => Unit)`]",
-    "doOnSubscribe(Action0)" -> "doOnSubscribe(=> Unit)",
-    "doOnUnsubscribe(Action0)" -> "doOnUnsubscribe(=> Unit)",
-    "doOnTerminate(Action0)" -> "doOnTerminate(=> Unit)",
+    "doOnSubscribe(Action0)" -> "doOnSubscribe(() => Unit)",
+    "doOnUnsubscribe(Action0)" -> "doOnUnsubscribe(() => Unit)",
+    "doOnTerminate(Action0)" -> "doOnTerminate(() => Unit)",
     "elementAtOrDefault(Int, T)" -> "elementAtOrDefault(Int, U)",
     "to(Func1[_ >: Observable[T], R])" -> "[use Scala implicit feature to extend `Observable`]",
-    "doAfterTerminate(Action0)" -> "doAfterTerminate(=> Unit)",
+    "doAfterTerminate(Action0)" -> "doAfterTerminate(() => Unit)",
     "first(Func1[_ >: T, Boolean])" -> commentForFirstWithPredicate,
     "firstOrDefault(T)" -> "firstOrElse(=> U)",
     "firstOrDefault(T, Func1[_ >: T, Boolean])" -> "[use `.filter(condition).firstOrElse(default)`]",
@@ -108,7 +108,7 @@ class ObservableCompletenessKit extends CompletenessKit {
     "groupBy(Func1[_ >: T, _ <: K], Func1[_ >: T, _ <: R], Func1[Action1[K], Map[K, Object]])" -> "[TODO]",
     "mergeWith(Observable[_ <: T])" -> "merge(Observable[U])",
     "ofType(Class[R])" -> "[use `filter(_.isInstanceOf[Class])`]",
-    "onBackpressureBuffer(Long, Action0)" -> "onBackpressureBuffer(Long, => Unit)",
+    "onBackpressureBuffer(Long, Action0)" -> "onBackpressureBuffer(Long, () => Unit)",
     "onBackpressureBuffer(Long, Action0, Strategy)" -> "[TODO]",
     "onErrorResumeNext(Func1[_ >: Throwable, _ <: Observable[_ <: T]])" -> "onErrorResumeNext(Throwable => Observable[U])",
     "onErrorResumeNext(Observable[_ <: T])" -> "onErrorResumeNext(Throwable => Observable[U])",