diff --git a/extensions/multibindings/src/com/google/inject/multibindings/OptionalBinder.java b/extensions/multibindings/src/com/google/inject/multibindings/OptionalBinder.java
index 4d4dfac..4a8a488 100644
--- a/extensions/multibindings/src/com/google/inject/multibindings/OptionalBinder.java
+++ b/extensions/multibindings/src/com/google/inject/multibindings/OptionalBinder.java
@@ -76,9 +76,11 @@
  * setBinding to a Provider that returns null will not cause OptionalBinder
  * to fall back to the setDefault binding.
  * 
- * <p>If neither setDefault nor setBinding are called, the optionals will be
- * absent.  Otherwise, the optionals will return present if they are bound
- * to a non-null value.
+ * <p>If neither setDefault nor setBinding are called, it will try to link to a
+ * user-supplied binding of the same type.  If no binding exists, the optionals
+ * will be absent.  Otherwise, if a user-supplied binding of that type exists,
+ * or if setBinding or setDefault are called, the optionals will return present
+ * if they are bound to a non-null value.
  *
  * <p>Values are resolved at injection time. If a value is bound to a
  * provider, that provider's get method will be called each time the optional
@@ -96,9 +98,18 @@
  * }</code></pre>
  *
  * <p>With this module, an {@link Optional}{@code <Renamer>} can now be
- * injected.  With no other bindings, the optional will be absent.  However,
- * once a user adds a binding:
+ * injected.  With no other bindings, the optional will be absent.
+ * Users can specify bindings in one of two ways:
  * 
+ * <p>Option 1:
+ * <pre><code>
+ * public class UserRenamerModule extends AbstractModule {
+ *   protected void configure() {
+ *     bind(Renamer.class).to(ReplacingRenamer.class);
+ *   }
+ * }</code></pre>
+ * 
+ * <p>or Option 2:
  * <pre><code>
  * public class UserRenamerModule extends AbstractModule {
  *   protected void configure() {
@@ -106,8 +117,8 @@
  *         .setBinding().to(ReplacingRenamer.class);
  *   }
  * }</code></pre>
- * .. then the {@code Optional<Renamer>} will be present and supply the
- * ReplacingRenamer.
+ * With both options, the {@code Optional<Renamer>} will be present and supply the
+ * ReplacingRenamer. 
  * 
  * <p>Default values can be supplied using:
  * <pre><code>
@@ -127,6 +138,24 @@
  *   }
  * }</code></pre>
  * ... which will override the default value.
+ * 
+ * <p>If one module uses setDefault the only way to override the default is to use setBinding.
+ * It is an error for a user to specify the binding without using OptionalBinder if
+ * setDefault or setBinding are called.  For example, 
+ * <pre><code>
+ * public class FrameworkModule extends AbstractModule {
+ *   protected void configure() {
+ *     OptionalBinder.newOptionalBinder(binder(), Key.get(String.class, LookupUrl.class))
+ *         .setDefault().to(DEFAULT_LOOKUP_URL);
+ *   }
+ * }
+ * public class UserLookupModule extends AbstractModule {
+ *   protected void configure() {
+ *     bind(Key.get(String.class, LookupUrl.class)).to(CUSTOM_LOOKUP_URL);
+ *   } 
+ * }</code></pre>
+ * ... would generate an error, because both the framework and the user are trying to bind
+ * {@code @LookupUrl String}. 
  *
  * @author sameb@google.com (Sam Berlin)
  */
@@ -257,7 +286,7 @@
      */
     private void addDirectTypeBinding(Binder binder) {
       binder.bind(typeKey).toProvider(new RealOptionalBinderProviderWithDependencies<T>(typeKey) {
-        public T get() {
+        @Override public T get() {
           Optional<Provider<T>> optional = optionalProviderT.get();
           if (optional.isPresent()) {
             return optional.get().get();
@@ -268,7 +297,7 @@
           return null; 
         }
 
-        public Set<Dependency<?>> getDependencies() {
+        @Override public Set<Dependency<?>> getDependencies() {
           return dependencies;
         }
       });
@@ -286,7 +315,7 @@
       return binder.bind(actualKey);
     }
 
-    public void configure(Binder binder) {
+    @Override public void configure(Binder binder) {
       checkConfiguration(!isInitialized(), "OptionalBinder was already initialized");
 
       binder.bind(optionalProviderKey).toProvider(
@@ -297,6 +326,7 @@
           RealOptionalBinder.this.binder = null;
           actualBinding = injector.getExistingBinding(actualKey);
           defaultBinding = injector.getExistingBinding(defaultKey);
+          Binding<T> userBinding = injector.getExistingBinding(typeKey);
           Binding<T> binding = null;
           if (actualBinding != null) {
             // TODO(sameb): Consider exposing an option that will allow
@@ -306,6 +336,12 @@
             binding = actualBinding;
           } else if (defaultBinding != null) {
             binding = defaultBinding;
+          } else if (userBinding != null) {
+            // If neither the actual or default is set, then we fallback
+            // to the value bound to the type itself and consider that the
+            // "actual binding" for the SPI.
+            binding = userBinding;
+            actualBinding = userBinding;
           }
           
           if (binding != null) {
@@ -321,11 +357,11 @@
           }
         }
         
-        public Optional<Provider<T>> get() {
+        @Override public Optional<Provider<T>> get() {
           return optional;
         }
 
-        public Set<Dependency<?>> getDependencies() {
+        @Override public Set<Dependency<?>> getDependencies() {
           return providerDependencies;
         }
       });
@@ -348,7 +384,7 @@
         super(typeKey);
       }
       
-      public Optional<T> get() {
+      @Override public Optional<T> get() {
         Optional<Provider<T>> optional = optionalProviderT.get();
         if (optional.isPresent()) {
           return Optional.fromNullable(optional.get().get());
@@ -357,11 +393,12 @@
         }
       }
 
-      public Set<Dependency<?>> getDependencies() {
+      @Override public Set<Dependency<?>> getDependencies() {
         return dependencies;
       }
 
       @SuppressWarnings("unchecked")
+      @Override
       public <B, R> R acceptExtensionVisitor(BindingTargetVisitor<B, R> visitor,
           ProviderInstanceBinding<? extends B> binding) {
         if (visitor instanceof MultibindingsTargetVisitor) {
@@ -371,11 +408,11 @@
         }
       }
 
-      public Key<Optional<T>> getKey() {
+      @Override public Key<Optional<T>> getKey() {
         return optionalKey;
       }
       
-      public Binding<?> getActualBinding() {
+      @Override public Binding<?> getActualBinding() {
         if (isInitialized()) {
           return actualBinding;
         } else {
@@ -384,7 +421,7 @@
         }
       }
       
-      public Binding<?> getDefaultBinding() {
+      @Override public Binding<?> getDefaultBinding() {
         if (isInitialized()) {
           return defaultBinding;
         } else {
@@ -393,7 +430,7 @@
         }
       }
 
-      public boolean containsElement(Element element) {
+      @Override public boolean containsElement(Element element) {
         Key<?> elementKey;
         if (element instanceof Binding) {
           elementKey = ((Binding<?>) element).getKey();
@@ -445,14 +482,12 @@
         this.equality = equality;
       }
 
-      @Override
-      public boolean equals(Object obj) {
+      @Override public boolean equals(Object obj) {
         return this.getClass() == obj.getClass()
             && equality.equals(((RealOptionalBinderProviderWithDependencies<?>) obj).equality);
       }
 
-      @Override
-      public int hashCode() {
+      @Override public int hashCode() {
         return equality.hashCode();
       }
     }
diff --git a/extensions/multibindings/test/com/google/inject/multibindings/OptionalBinderTest.java b/extensions/multibindings/test/com/google/inject/multibindings/OptionalBinderTest.java
index f4c46ca..d2bceb8 100644
--- a/extensions/multibindings/test/com/google/inject/multibindings/OptionalBinderTest.java
+++ b/extensions/multibindings/test/com/google/inject/multibindings/OptionalBinderTest.java
@@ -126,10 +126,10 @@
         injector.getInstance(Key.get(optionalOfJavaxProviderString));
     assertFalse(optionalJxP.isPresent());
     
-    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, null, null);
+    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, null, null, null);
   }
   
-  public void testAbsentWithUserBoundValue() {
+  public void testUsesUserBoundValue() {
     Module module = new AbstractModule() {
       @Override protected void configure() {
         OptionalBinder.newOptionalBinder(binder(), String.class);
@@ -141,16 +141,22 @@
     assertEquals("foo", injector.getInstance(String.class));
     
     Optional<String> optional = injector.getInstance(Key.get(optionalOfString));
-    assertFalse(optional.isPresent());
+    assertEquals("foo", optional.get());
     
     Optional<Provider<String>> optionalP = injector.getInstance(Key.get(optionalOfProviderString));
-    assertFalse(optionalP.isPresent());
+    assertEquals("foo", optionalP.get().get());
     
     Optional<javax.inject.Provider<String>> optionalJxP =
         injector.getInstance(Key.get(optionalOfJavaxProviderString));
-    assertFalse(optionalJxP.isPresent());
+    assertEquals("foo", optionalJxP.get().get());
     
-    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, null, null);
+    assertOptionalVisitor(stringKey,
+        setOf(module),
+        VisitType.BOTH,
+        0,
+        null,
+        null,
+        providerInstance("foo"));
   }
   
   public void testSetDefault() {
@@ -175,7 +181,7 @@
     assertTrue(optionalJxP.isPresent());
     assertEquals("a", optionalJxP.get().get());
 
-    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, instance("a"), null);
+    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, instance("a"), null, null);
   }
   
   public void testSetBinding() {
@@ -200,7 +206,7 @@
     assertTrue(optionalJxP.isPresent());
     assertEquals("a", optionalJxP.get().get());
     
-    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, null, instance("a"));
+    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, null, instance("a"), null);
   }
   
   public void testSetBindingOverridesDefault() {
@@ -233,7 +239,8 @@
         VisitType.BOTH,
         0,
         instance("a"),
-        instance("b"));
+        instance("b"),
+        null);
   }
   
   public void testSpreadAcrossModules() {
@@ -274,7 +281,8 @@
         VisitType.BOTH,
         0,
         instance("a"),
-        instance("b"));
+        instance("b"),
+        null);
   }
   
   public void testExactSameBindingCollapses_defaults() {
@@ -302,7 +310,7 @@
     assertTrue(optionalJxP.isPresent());
     assertEquals("a", optionalJxP.get().get());
 
-    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, instance("a"), null);
+    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, instance("a"), null, null);
   }
   
   public void testExactSameBindingCollapses_actual() {
@@ -330,7 +338,7 @@
     assertTrue(optionalJxP.isPresent());
     assertEquals("a", optionalJxP.get().get());
 
-    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, null, instance("a"));
+    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 0, null, instance("a"), null);
   }
   
   public void testDifferentBindingsFail_defaults() {
@@ -443,7 +451,8 @@
         VisitType.BOTH,
         0,
         instance("a"),
-        instance("b"));
+        instance("b"),
+        null);
   }
   
   public void testMultipleDifferentOptionals() {
@@ -464,10 +473,10 @@
     assertEquals("b", injector.getInstance(bKey));
     assertEquals("c", injector.getInstance(cKey));
     
-    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 3, instance("a"), null);
-    assertOptionalVisitor(intKey, setOf(module), VisitType.BOTH, 3, instance(1), null);
-    assertOptionalVisitor(bKey, setOf(module), VisitType.BOTH, 3, instance("b"), null);
-    assertOptionalVisitor(cKey, setOf(module), VisitType.BOTH, 3, instance("c"), null);
+    assertOptionalVisitor(stringKey, setOf(module), VisitType.BOTH, 3, instance("a"), null, null);
+    assertOptionalVisitor(intKey, setOf(module), VisitType.BOTH, 3, instance(1), null, null);
+    assertOptionalVisitor(bKey, setOf(module), VisitType.BOTH, 3, instance("b"), null, null);
+    assertOptionalVisitor(cKey, setOf(module), VisitType.BOTH, 3, instance("c"), null, null);
   }
   
   public void testOptionalIsAppropriatelyLazy() {
@@ -533,6 +542,7 @@
         VisitType.BOTH,
         0,
         SpiUtils.<String>providerInstance(null),
+        null,
         null);
   }
   
@@ -563,7 +573,8 @@
         VisitType.BOTH,
         0,
         null,
-        SpiUtils.<String>providerInstance(null));
+        SpiUtils.<String>providerInstance(null),
+        null);
   }
   
   // TODO(sameb): Maybe change this?
@@ -595,7 +606,8 @@
         VisitType.BOTH,
         0,
         instance("a"),
-        SpiUtils.<String>providerInstance(null));
+        SpiUtils.<String>providerInstance(null),
+        null);
   }
 
   public void testSourceLinesInException() {
@@ -699,7 +711,8 @@
         VisitType.BOTH,
         0,
         instance("A"),
-        instance("B"));
+        instance("B"),
+        null);
   }
 
   public void testModuleOverrideRepeatedInstalls_toKey() {
@@ -726,7 +739,8 @@
         VisitType.BOTH,
         0,
         linked(aKey),
-        linked(bKey));
+        linked(bKey),
+        null);
   }
 
   public void testModuleOverrideRepeatedInstalls_toProviderInstance() {
@@ -751,7 +765,8 @@
         VisitType.BOTH,
         0,
         providerInstance("A"),
-        providerInstance("B"));
+        providerInstance("B"),
+        null);
   }
 
   private static class AStringProvider implements Provider<String> {
@@ -785,7 +800,8 @@
         VisitType.BOTH,
         0,
         providerKey(Key.get(AStringProvider.class)),
-        providerKey(Key.get(BStringProvider.class)));
+        providerKey(Key.get(BStringProvider.class)),
+        null);
   }
 
   private static class StringGrabber {
diff --git a/extensions/multibindings/test/com/google/inject/multibindings/SpiUtils.java b/extensions/multibindings/test/com/google/inject/multibindings/SpiUtils.java
index 9517425..7e34ffe 100644
--- a/extensions/multibindings/test/com/google/inject/multibindings/SpiUtils.java
+++ b/extensions/multibindings/test/com/google/inject/multibindings/SpiUtils.java
@@ -466,32 +466,43 @@
    * @param expectedOtherOptionalBindings the # of other optional bindings we expect to see.
    * @param expectedDefault the expected default binding, or null if none
    * @param expectedActual the expected actual binding, or null if none
+   * @param expectedUserLinkedActual the user binding that is the actual binding, used if
+   *        neither the default nor actual are set and a user binding existed for the type.
    */
   static <T> void assertOptionalVisitor(Key<T> keyType,
       Iterable<? extends Module> modules,
       VisitType visitType,
       int expectedOtherOptionalBindings,
       BindResult<?> expectedDefault,
-      BindResult<?> expectedActual) {
+      BindResult<?> expectedActual,
+      BindResult<?> expectedUserLinkedActual) {
     if (visitType == null) {
       fail("must test something");
     }
 
     if (visitType == BOTH || visitType == INJECTOR) {
       optionalInjectorTest(keyType, modules, expectedOtherOptionalBindings, expectedDefault,
-          expectedActual);
+          expectedActual, expectedUserLinkedActual);
     }
 
     if (visitType == BOTH || visitType == MODULE) {
       optionalModuleTest(keyType, modules, expectedOtherOptionalBindings, expectedDefault,
-          expectedActual);
+          expectedActual, expectedUserLinkedActual);
     }
   }
 
   @SuppressWarnings("unchecked")
-  private static <T> void optionalInjectorTest(Key<T> keyType, Iterable<? extends Module> modules,
-      int expectedOtherOptionalBindings, BindResult<?> expectedDefault,
-      BindResult<?> expectedActual) {
+  private static <T> void optionalInjectorTest(Key<T> keyType,
+      Iterable<? extends Module> modules,
+      int expectedOtherOptionalBindings,
+      BindResult<?> expectedDefault,
+      BindResult<?> expectedActual,
+      BindResult<?> expectedUserLinkedActual) {
+    if (expectedUserLinkedActual != null) {
+      assertNull("cannot have actual if expecting user binding", expectedActual);
+      assertNull("cannot have default if expecting user binding", expectedDefault);
+    }
+    
     Key<Optional<T>> optionalKey =
         keyType.ofType(OptionalBinder.optionalOf(keyType.getTypeLiteral()));
     Injector injector = Guice.createInjector(modules);
@@ -510,12 +521,16 @@
           matches(optionalBinder.getDefaultBinding(), expectedDefault));
     }
 
-    if (expectedActual == null) {
+    if (expectedActual == null && expectedUserLinkedActual == null) {
       assertNull(optionalBinder.getActualBinding());
-    } else {
+    } else if (expectedActual != null) {
       assertTrue("expectedActual: " + expectedActual + ", actualActual: "
           + optionalBinder.getActualBinding(),
           matches(optionalBinder.getActualBinding(), expectedActual));
+    } else if (expectedUserLinkedActual != null) {
+      assertTrue("expectedUserLinkedActual: " + expectedUserLinkedActual + ", actualActual: "
+          + optionalBinder.getActualBinding(),
+          matches(optionalBinder.getActualBinding(), expectedUserLinkedActual));
     }
 
 
@@ -582,9 +597,16 @@
   }
 
   @SuppressWarnings("unchecked")
-  private static <T> void optionalModuleTest(Key<T> keyType, Iterable<? extends Module> modules,
-      int expectedOtherOptionalBindings, BindResult<?> expectedDefault,
-      BindResult<?> expectedActual) {
+  private static <T> void optionalModuleTest(Key<T> keyType,
+      Iterable<? extends Module> modules,
+      int expectedOtherOptionalBindings,
+      BindResult<?> expectedDefault,
+      BindResult<?> expectedActual,
+      BindResult<?> expectedUserLinkedActual) {
+    if (expectedUserLinkedActual != null) {
+      assertNull("cannot have actual if expecting user binding", expectedActual);
+      assertNull("cannot have default if expecting user binding", expectedDefault);
+    }
     Set<Element> elements = ImmutableSet.copyOf(Elements.getElements(modules));
     Map<Key<?>, Binding<?>> indexed = index(elements);
     Key<Optional<T>> optionalKey =