diff --git a/src/main/java/rx/Observable.java b/src/main/java/rx/Observable.java
index ebe421a120..02142ec6ce 100644
--- a/src/main/java/rx/Observable.java
+++ b/src/main/java/rx/Observable.java
@@ -119,7 +119,7 @@ public interface Operator<R, T> extends Func1<Subscriber<? super R>, Subscriber<
      * @since (if this graduates from Experimental/Beta to supported, replace this parenthetical with the release number)
      */
     @Experimental
-    public <R> R x(Func1<? super OnSubscribe<T>, ? extends R> conversion) {
+    public <R> R extend(Func1<? super OnSubscribe<T>, ? extends R> conversion) {
         return conversion.call(new OnSubscribe<T>() {
             @Override
             public void call(Subscriber<? super T> subscriber) {
diff --git a/src/test/java/rx/ObservableConversionTest.java b/src/test/java/rx/ObservableConversionTest.java
index 543c44780b..31880ea599 100644
--- a/src/test/java/rx/ObservableConversionTest.java
+++ b/src/test/java/rx/ObservableConversionTest.java
@@ -155,7 +155,7 @@ public void onNext(String t) {
             }});
         List<Object> crewOfBattlestarGalactica = Arrays.asList(new Object[] {"William Adama", "Laura Roslin", "Lee Adama", new Cylon()});
         Observable.from(crewOfBattlestarGalactica)
-            .x(new ConvertToCylonDetector<Object>())
+            .extend(new ConvertToCylonDetector<Object>())
             .beep(new Func1<Object, Boolean>(){
                 @Override
                 public Boolean call(Object t) {
@@ -199,7 +199,7 @@ public Integer call(Integer k) {
                                         return i + k;
                                     }});
                     }})
-                    .x(new Func1<OnSubscribe<Integer>, ConcurrentLinkedQueue<Integer>>() {
+                    .extend(new Func1<OnSubscribe<Integer>, ConcurrentLinkedQueue<Integer>>() {
                         @Override
                         public ConcurrentLinkedQueue<Integer> call(OnSubscribe<Integer> onSubscribe) {
                             final ConcurrentLinkedQueue<Integer> q = new ConcurrentLinkedQueue<Integer>();
diff --git a/src/test/java/rx/ObservableTests.java b/src/test/java/rx/ObservableTests.java
index 55e43896d3..d59e8c41a9 100644
--- a/src/test/java/rx/ObservableTests.java
+++ b/src/test/java/rx/ObservableTests.java
@@ -1161,7 +1161,7 @@ public void testForEachWithNull() {
     public void testExtend() {
         final TestSubscriber<Object> subscriber = new TestSubscriber<Object>();
         final Object value = new Object();
-        Observable.just(value).x(new Func1<OnSubscribe<Object>,Object>(){
+        Observable.just(value).extend(new Func1<OnSubscribe<Object>,Object>(){
             @Override
             public Object call(OnSubscribe<Object> onSubscribe) {
                 onSubscribe.call(subscriber);