diff --git a/src/main/java/io/reactivex/internal/observers/CallbackCompletableObserver.java b/src/main/java/io/reactivex/internal/observers/CallbackCompletableObserver.java
index 1ad562398d..c09d4df14a 100644
--- a/src/main/java/io/reactivex/internal/observers/CallbackCompletableObserver.java
+++ b/src/main/java/io/reactivex/internal/observers/CallbackCompletableObserver.java
@@ -20,12 +20,12 @@
 import io.reactivex.exceptions.*;
 import io.reactivex.functions.*;
 import io.reactivex.internal.disposables.DisposableHelper;
-import io.reactivex.observers.CompositeObserver;
+import io.reactivex.observers.LambdaConsumerIntrospection;
 import io.reactivex.plugins.RxJavaPlugins;
 
 public final class CallbackCompletableObserver
 extends AtomicReference<Disposable>
-        implements CompletableObserver, Disposable, Consumer<Throwable>, CompositeObserver {
+        implements CompletableObserver, Disposable, Consumer<Throwable>, LambdaConsumerIntrospection {
 
 
     private static final long serialVersionUID = -4361286194466301354L;
@@ -86,7 +86,7 @@ public boolean isDisposed() {
     }
 
     @Override
-    public boolean onErrorImplemented() {
+    public boolean hasCustomOnError() {
         return onError == this;
     }
 }
diff --git a/src/main/java/io/reactivex/internal/observers/ConsumerSingleObserver.java b/src/main/java/io/reactivex/internal/observers/ConsumerSingleObserver.java
index 89162dcd6f..c1db45f7af 100644
--- a/src/main/java/io/reactivex/internal/observers/ConsumerSingleObserver.java
+++ b/src/main/java/io/reactivex/internal/observers/ConsumerSingleObserver.java
@@ -21,12 +21,12 @@
 import io.reactivex.functions.Consumer;
 import io.reactivex.internal.disposables.*;
 import io.reactivex.internal.functions.Functions;
-import io.reactivex.observers.CompositeObserver;
+import io.reactivex.observers.LambdaConsumerIntrospection;
 import io.reactivex.plugins.RxJavaPlugins;
 
 public final class ConsumerSingleObserver<T>
 extends AtomicReference<Disposable>
-implements SingleObserver<T>, Disposable, CompositeObserver {
+implements SingleObserver<T>, Disposable, LambdaConsumerIntrospection {
 
 
     private static final long serialVersionUID = -7012088219455310787L;
@@ -78,7 +78,7 @@ public boolean isDisposed() {
     }
 
     @Override
-    public boolean onErrorImplemented() {
+    public boolean hasCustomOnError() {
         return onError == Functions.ON_ERROR_MISSING;
     }
 }
diff --git a/src/main/java/io/reactivex/internal/observers/EmptyCompletableObserver.java b/src/main/java/io/reactivex/internal/observers/EmptyCompletableObserver.java
index ad4ae85a99..d6320911c3 100644
--- a/src/main/java/io/reactivex/internal/observers/EmptyCompletableObserver.java
+++ b/src/main/java/io/reactivex/internal/observers/EmptyCompletableObserver.java
@@ -19,12 +19,12 @@
 import io.reactivex.disposables.Disposable;
 import io.reactivex.exceptions.OnErrorNotImplementedException;
 import io.reactivex.internal.disposables.DisposableHelper;
-import io.reactivex.observers.CompositeObserver;
+import io.reactivex.observers.LambdaConsumerIntrospection;
 import io.reactivex.plugins.RxJavaPlugins;
 
 public final class EmptyCompletableObserver
 extends AtomicReference<Disposable>
-implements CompletableObserver, Disposable, CompositeObserver {
+implements CompletableObserver, Disposable, LambdaConsumerIntrospection {
 
 
     private static final long serialVersionUID = -7545121636549663526L;
@@ -57,7 +57,7 @@ public void onSubscribe(Disposable d) {
     }
 
     @Override
-    public boolean onErrorImplemented() {
+    public boolean hasCustomOnError() {
         return true;
     }
 }
diff --git a/src/main/java/io/reactivex/internal/observers/LambdaObserver.java b/src/main/java/io/reactivex/internal/observers/LambdaObserver.java
index 7bb7c8f708..3cc192a8f9 100644
--- a/src/main/java/io/reactivex/internal/observers/LambdaObserver.java
+++ b/src/main/java/io/reactivex/internal/observers/LambdaObserver.java
@@ -21,11 +21,11 @@
 import io.reactivex.functions.*;
 import io.reactivex.internal.disposables.DisposableHelper;
 import io.reactivex.internal.functions.Functions;
-import io.reactivex.observers.CompositeObserver;
+import io.reactivex.observers.LambdaConsumerIntrospection;
 import io.reactivex.plugins.RxJavaPlugins;
 
 public final class LambdaObserver<T> extends AtomicReference<Disposable>
-        implements Observer<T>, Disposable, CompositeObserver {
+        implements Observer<T>, Disposable, LambdaConsumerIntrospection {
 
     private static final long serialVersionUID = -7251123623727029452L;
     final Consumer<? super T> onNext;
@@ -106,7 +106,7 @@ public boolean isDisposed() {
     }
 
     @Override
-    public boolean onErrorImplemented() {
+    public boolean hasCustomOnError() {
         return onError == Functions.ON_ERROR_MISSING;
     }
 }
diff --git a/src/main/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserver.java b/src/main/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserver.java
index e5486f57fe..321e9c3748 100644
--- a/src/main/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserver.java
+++ b/src/main/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserver.java
@@ -21,7 +21,7 @@
 import io.reactivex.functions.*;
 import io.reactivex.internal.disposables.DisposableHelper;
 import io.reactivex.internal.functions.Functions;
-import io.reactivex.observers.CompositeObserver;
+import io.reactivex.observers.LambdaConsumerIntrospection;
 import io.reactivex.plugins.RxJavaPlugins;
 
 /**
@@ -31,7 +31,7 @@
  */
 public final class MaybeCallbackObserver<T>
 extends AtomicReference<Disposable>
-implements MaybeObserver<T>, Disposable, CompositeObserver {
+implements MaybeObserver<T>, Disposable, LambdaConsumerIntrospection {
 
 
     private static final long serialVersionUID = -6076952298809384986L;
@@ -99,7 +99,7 @@ public void onComplete() {
     }
 
     @Override
-    public boolean onErrorImplemented() {
+    public boolean hasCustomOnError() {
         return onError == Functions.ON_ERROR_MISSING;
     }
 }
diff --git a/src/main/java/io/reactivex/internal/subscribers/LambdaSubscriber.java b/src/main/java/io/reactivex/internal/subscribers/LambdaSubscriber.java
index 2ff33564e9..f6b85c6774 100644
--- a/src/main/java/io/reactivex/internal/subscribers/LambdaSubscriber.java
+++ b/src/main/java/io/reactivex/internal/subscribers/LambdaSubscriber.java
@@ -16,7 +16,7 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 import io.reactivex.internal.functions.Functions;
-import io.reactivex.observers.CompositeObserver;
+import io.reactivex.observers.LambdaConsumerIntrospection;
 import org.reactivestreams.Subscription;
 
 import io.reactivex.FlowableSubscriber;
@@ -27,7 +27,7 @@
 import io.reactivex.plugins.RxJavaPlugins;
 
 public final class LambdaSubscriber<T> extends AtomicReference<Subscription>
-        implements FlowableSubscriber<T>, Subscription, Disposable, CompositeObserver {
+        implements FlowableSubscriber<T>, Subscription, Disposable, LambdaConsumerIntrospection {
 
     private static final long serialVersionUID = -7251123623727029452L;
     final Consumer<? super T> onNext;
@@ -120,7 +120,7 @@ public void cancel() {
     }
 
     @Override
-    public boolean onErrorImplemented() {
+    public boolean hasCustomOnError() {
         return onError == Functions.ON_ERROR_MISSING;
     }
 }
diff --git a/src/main/java/io/reactivex/observers/CompositeObserver.java b/src/main/java/io/reactivex/observers/LambdaConsumerIntrospection.java
similarity index 73%
rename from src/main/java/io/reactivex/observers/CompositeObserver.java
rename to src/main/java/io/reactivex/observers/LambdaConsumerIntrospection.java
index a3a31d9fd8..a7371d018e 100644
--- a/src/main/java/io/reactivex/observers/CompositeObserver.java
+++ b/src/main/java/io/reactivex/observers/LambdaConsumerIntrospection.java
@@ -6,18 +6,18 @@
  * An interface that indicates that the implementing type is composed of individual components and exposes information
  * about their behavior.
  *
- * <p><em>NOTE:</em> This is considered a read-only public API and is not intended to be implemented by consumers.
+ * <p><em>NOTE:</em> This is considered a read-only public API and is not intended to be implemented externally.
  *
  * @since 2.1.4 - experimental
  */
 @Experimental
-public interface CompositeObserver {
+public interface LambdaConsumerIntrospection {
 
     /**
-     * @return {@code true} if a concrete error consumer implementation was supplied. Returns {@code false} if the
+     * @return {@code true} if a custom onError consumer implementation was supplied. Returns {@code false} if the
      * implementation is missing an error consumer and thus using a throwing default implementation.
      */
     @Experimental
-    boolean onErrorImplemented();
+    boolean hasCustomOnError();
 
 }
diff --git a/src/test/java/io/reactivex/internal/observers/CallbackCompletableObserverTest.java b/src/test/java/io/reactivex/internal/observers/CallbackCompletableObserverTest.java
index acf74911de..000adee8e3 100644
--- a/src/test/java/io/reactivex/internal/observers/CallbackCompletableObserverTest.java
+++ b/src/test/java/io/reactivex/internal/observers/CallbackCompletableObserverTest.java
@@ -11,7 +11,7 @@ public final class CallbackCompletableObserverTest {
     public void hasMissingErrorConsumer() {
         CallbackCompletableObserver o = new CallbackCompletableObserver(Functions.EMPTY_ACTION);
 
-        assertTrue(o.onErrorImplemented());
+        assertTrue(o.hasCustomOnError());
     }
 
     @Test
@@ -19,7 +19,7 @@ public void isNotMissingErrorConsumer() {
         CallbackCompletableObserver o = new CallbackCompletableObserver(Functions.<Throwable>emptyConsumer(),
                 Functions.EMPTY_ACTION);
 
-        assertFalse(o.onErrorImplemented());
+        assertFalse(o.hasCustomOnError());
     }
 
 }
diff --git a/src/test/java/io/reactivex/internal/observers/ConsumerSingleObserverTest.java b/src/test/java/io/reactivex/internal/observers/ConsumerSingleObserverTest.java
index 7fd7fe5c96..dceeec2ecc 100644
--- a/src/test/java/io/reactivex/internal/observers/ConsumerSingleObserverTest.java
+++ b/src/test/java/io/reactivex/internal/observers/ConsumerSingleObserverTest.java
@@ -12,7 +12,7 @@ public void hasMissingErrorConsumer() {
         ConsumerSingleObserver<Integer> o = new ConsumerSingleObserver<Integer>(Functions.<Integer>emptyConsumer(),
                 Functions.ON_ERROR_MISSING);
 
-        assertTrue(o.onErrorImplemented());
+        assertTrue(o.hasCustomOnError());
     }
 
     @Test
@@ -20,7 +20,7 @@ public void isNotMissingErrorConsumer() {
         ConsumerSingleObserver<Integer> o = new ConsumerSingleObserver<Integer>(Functions.<Integer>emptyConsumer(),
                 Functions.<Throwable>emptyConsumer());
 
-        assertFalse(o.onErrorImplemented());
+        assertFalse(o.hasCustomOnError());
     }
 
 }
diff --git a/src/test/java/io/reactivex/internal/observers/EmptyCompletableObserverTest.java b/src/test/java/io/reactivex/internal/observers/EmptyCompletableObserverTest.java
index bd8d696aa0..dcecac7731 100644
--- a/src/test/java/io/reactivex/internal/observers/EmptyCompletableObserverTest.java
+++ b/src/test/java/io/reactivex/internal/observers/EmptyCompletableObserverTest.java
@@ -10,6 +10,6 @@ public final class EmptyCompletableObserverTest {
     public void hasMissingErrorConsumer() {
         EmptyCompletableObserver o = new EmptyCompletableObserver();
 
-        assertTrue(o.onErrorImplemented());
+        assertTrue(o.hasCustomOnError());
     }
 }
diff --git a/src/test/java/io/reactivex/internal/observers/LambdaObserverTest.java b/src/test/java/io/reactivex/internal/observers/LambdaObserverTest.java
index 4d7ac21bac..23e100d992 100644
--- a/src/test/java/io/reactivex/internal/observers/LambdaObserverTest.java
+++ b/src/test/java/io/reactivex/internal/observers/LambdaObserverTest.java
@@ -351,7 +351,7 @@ public void hasMissingErrorConsumer() {
                 Functions.EMPTY_ACTION,
                 Functions.<Disposable>emptyConsumer());
 
-        assertTrue(o.onErrorImplemented());
+        assertTrue(o.hasCustomOnError());
     }
 
     @Test
@@ -361,6 +361,6 @@ public void isNotMissingErrorConsumer() {
                 Functions.EMPTY_ACTION,
                 Functions.<Disposable>emptyConsumer());
 
-        assertFalse(o.onErrorImplemented());
+        assertFalse(o.hasCustomOnError());
     }
 }
diff --git a/src/test/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserverTest.java b/src/test/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserverTest.java
index 79c7271d1a..b022e0a823 100644
--- a/src/test/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserverTest.java
+++ b/src/test/java/io/reactivex/internal/operators/maybe/MaybeCallbackObserverTest.java
@@ -127,7 +127,7 @@ public void hasMissingErrorConsumer() {
                 Functions.ON_ERROR_MISSING,
                 Functions.EMPTY_ACTION);
 
-        assertTrue(o.onErrorImplemented());
+        assertTrue(o.hasCustomOnError());
     }
 
     @Test
@@ -136,6 +136,6 @@ public void isNotMissingErrorConsumer() {
                 Functions.<Throwable>emptyConsumer(),
                 Functions.EMPTY_ACTION);
 
-        assertFalse(o.onErrorImplemented());
+        assertFalse(o.hasCustomOnError());
     }
 }
diff --git a/src/test/java/io/reactivex/internal/subscribers/LambdaSubscriberTest.java b/src/test/java/io/reactivex/internal/subscribers/LambdaSubscriberTest.java
index d64dbe62b5..35cec65031 100644
--- a/src/test/java/io/reactivex/internal/subscribers/LambdaSubscriberTest.java
+++ b/src/test/java/io/reactivex/internal/subscribers/LambdaSubscriberTest.java
@@ -356,7 +356,7 @@ public void hasMissingErrorConsumer() {
                 Functions.EMPTY_ACTION,
                 FlowableInternalHelper.RequestMax.INSTANCE);
 
-        assertTrue(o.onErrorImplemented());
+        assertTrue(o.hasCustomOnError());
     }
 
     @Test
@@ -366,6 +366,6 @@ public void isNotMissingErrorConsumer() {
                 Functions.EMPTY_ACTION,
                 FlowableInternalHelper.RequestMax.INSTANCE);
 
-        assertFalse(o.onErrorImplemented());
+        assertFalse(o.hasCustomOnError());
     }
 }