diff --git a/runtime/vm/code_generator_test.cc b/runtime/vm/code_generator_test.cc
index a610f86c05f..699a746ebf2 100644
--- a/runtime/vm/code_generator_test.cc
+++ b/runtime/vm/code_generator_test.cc
@@ -488,8 +488,14 @@ CODEGEN_TEST_RAW_RUN(AllocateNewObjectCodegen, function) {
   Object& result = Object::Handle();
   result = DartEntry::InvokeStatic(function, arguments, kNoArgumentNames);
   EXPECT(!result.IsError());
-  const Library& app_lib = Library::Handle(
-      Isolate::Current()->object_store()->registered_libraries());
+  const GrowableObjectArray& libs =  GrowableObjectArray::Handle(
+      Isolate::Current()->object_store()->libraries());
+  ASSERT(!libs.IsNull());
+  // App lib is the last one that was loaded.
+  intptr_t num_libs = libs.Length();
+  Library& app_lib = Library::Handle();
+  app_lib ^= libs.At(num_libs - 1);
+  ASSERT(!app_lib.IsNull());
   const Class& cls = Class::Handle(
       app_lib.LookupClass(String::Handle(String::NewSymbol("A"))));
   EXPECT_EQ(cls.raw(), result.clazz());
diff --git a/runtime/vm/dart_api_impl_test.cc b/runtime/vm/dart_api_impl_test.cc
index 70b84e6a398..0170bfd90e0 100644
--- a/runtime/vm/dart_api_impl_test.cc
+++ b/runtime/vm/dart_api_impl_test.cc
@@ -4240,7 +4240,7 @@ TEST_CASE(ImportLibrary3) {
   result = Dart_Invoke(result, Dart_NewString("main"), 0, NULL);
   EXPECT(Dart_IsError(result));
   EXPECT_STREQ("Duplicate definition : 'foo' is defined in"
-               " 'library1.dart' and 'library2.dart'\n",
+               " 'library2.dart' and 'library1.dart'\n",
                Dart_GetError(result));
 }
 
@@ -4312,7 +4312,7 @@ TEST_CASE(ImportLibrary4) {
   result = Dart_Invoke(result, Dart_NewString("main"), 0, NULL);
   EXPECT(Dart_IsError(result));
   EXPECT_STREQ("Duplicate definition : 'fooC' is defined in"
-               " 'libraryF.dart' and 'libraryC.dart'\n",
+               " 'libraryC.dart' and 'libraryF.dart'\n",
                Dart_GetError(result));
 }
 
diff --git a/runtime/vm/debugger.cc b/runtime/vm/debugger.cc
index dcfcb402bfd..11daaa7aaeb 100644
--- a/runtime/vm/debugger.cc
+++ b/runtime/vm/debugger.cc
@@ -725,13 +725,14 @@ SourceBreakpoint* Debugger::SetBreakpointAtLine(const String& script_url,
                                           intptr_t line_number) {
   Library& lib = Library::Handle();
   Script& script = Script::Handle();
-  lib = isolate_->object_store()->registered_libraries();
-  while (!lib.IsNull()) {
+  const GrowableObjectArray& libs =
+      GrowableObjectArray::Handle(isolate_->object_store()->libraries());
+  for (int i = 0; i < libs.Length(); i++) {
+    lib ^= libs.At(i);
     script = lib.LookupScript(script_url);
     if (!script.IsNull()) {
       break;
     }
-    lib = lib.next_registered();
   }
   if (script.IsNull()) {
     if (verbose) {
diff --git a/runtime/vm/debugger_api_impl.cc b/runtime/vm/debugger_api_impl.cc
index 70ae2517c57..b6da4315f8a 100644
--- a/runtime/vm/debugger_api_impl.cc
+++ b/runtime/vm/debugger_api_impl.cc
@@ -498,26 +498,21 @@ DART_EXPORT Dart_Handle Dart_GetLibraryURLs() {
   ASSERT(isolate != NULL);
   DARTSCOPE(isolate);
 
-  // Find out how many libraries are loaded in this isolate.
-  int num_libs = 0;
-  Library &lib = Library::Handle();
-  lib = isolate->object_store()->registered_libraries();
-  while (!lib.IsNull()) {
-    num_libs++;
-    lib = lib.next_registered();
-  }
+  const GrowableObjectArray& libs =
+      GrowableObjectArray::Handle(isolate->object_store()->libraries());
+  int num_libs = libs.Length();
 
   // Create new list and populate with the url of loaded libraries.
-  const Array& library_list = Array::Handle(Array::New(num_libs));
-  lib = isolate->object_store()->registered_libraries();
+  Library &lib = Library::Handle();
   String& lib_url = String::Handle();
+  const Array& library_url_list = Array::Handle(Array::New(num_libs));
   for (int i = 0; i < num_libs; i++) {
+    lib ^= libs.At(i);
     ASSERT(!lib.IsNull());
     lib_url = lib.url();
-    library_list.SetAt(i, lib_url);
-    lib = lib.next_registered();
+    library_url_list.SetAt(i, lib_url);
   }
-  return Api::NewHandle(isolate, library_list.raw());
+  return Api::NewHandle(isolate, library_url_list.raw());
 }
 
 }  // namespace dart
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index 6b895245f71..ce70a9a5c4f 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -324,10 +324,12 @@ void Isolate::PrintInvokedFunctions() {
   ASSERT(this == Isolate::Current());
   Zone zone(this);
   HandleScope handle_scope(this);
+  const GrowableObjectArray& libraries =
+      GrowableObjectArray::Handle(object_store()->libraries());
   Library& library = Library::Handle();
-  library = object_store()->registered_libraries();
   GrowableArray<const Function*> invoked_functions;
-  while (!library.IsNull()) {
+  for (int i = 0; i < libraries.Length(); i++) {
+    library ^= libraries.At(i);
     Class& cls = Class::Handle();
     ClassDictionaryIterator iter(library);
     while (iter.HasNext()) {
@@ -339,7 +341,6 @@ void Isolate::PrintInvokedFunctions() {
       cls ^= anon_classes.At(i);
       AddFunctionsFromClass(cls, &invoked_functions);
     }
-    library = library.next_registered();
   }
   invoked_functions.Sort(MostUsedFunctionFirst);
   for (int i = 0; i < invoked_functions.length(); i++) {
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 5c592a684a5..96162fc4e7e 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -497,6 +497,11 @@ RawError* Object::Init(Isolate* isolate) {
   cls = Class::New<OneByteString>();
   object_store->set_one_byte_string_class(cls);
 
+  // Set up the libraries array before initializing the core library.
+  const GrowableObjectArray& libraries =
+      GrowableObjectArray::Handle(GrowableObjectArray::New(Heap::kOld));
+  object_store->set_libraries(libraries);
+
   // Basic infrastructure has been setup, initialize the class dictionary.
   Library::InitCoreLibrary(isolate);
   Library& core_lib = Library::Handle(Library::CoreLibrary());
@@ -5306,7 +5311,6 @@ RawLibrary* Library::NewLibraryHelper(const String& url,
   result.raw_ptr()->anonymous_classes_ = Array::Empty();
   result.raw_ptr()->num_anonymous_ = 0;
   result.raw_ptr()->imports_ = Array::Empty();
-  result.raw_ptr()->next_registered_ = Library::null();
   result.raw_ptr()->loaded_scripts_ = Array::null();
   result.set_native_entry_resolver(NULL);
   result.raw_ptr()->corelib_imported_ = true;
@@ -5404,32 +5408,34 @@ RawLibrary* Library::LookupLibrary(const String &url) {
   Isolate* isolate = Isolate::Current();
   Library& lib = Library::Handle(isolate, Library::null());
   String& lib_url = String::Handle(isolate, String::null());
-  lib = isolate->object_store()->registered_libraries();
-  while (!lib.IsNull()) {
+  GrowableObjectArray& libs = GrowableObjectArray::Handle(
+      isolate, isolate->object_store()->libraries());
+  for (int i = 0; i < libs.Length(); i++) {
+    lib ^= libs.At(i);
     lib_url = lib.url();
     if (lib_url.Equals(url)) {
       return lib.raw();
     }
-    lib = lib.next_registered();
   }
   return Library::null();
 }
 
 
 RawString* Library::CheckForDuplicateDefinition() {
-  Library& lib = Library::Handle();
   Isolate* isolate = Isolate::Current();
   ASSERT(isolate != NULL);
   ObjectStore* object_store = isolate->object_store();
   ASSERT(object_store != NULL);
-  lib ^= object_store->registered_libraries();
+  const GrowableObjectArray& libs =
+      GrowableObjectArray::Handle(object_store->libraries());
+  Library& lib = Library::Handle();
   String& error_message = String::Handle();
-  while (!lib.IsNull()) {
+  for (int i = 0; i < libs.Length(); i++) {
+    lib ^= libs.At(i);
     error_message = lib.FindDuplicateDefinition();
     if (!error_message.IsNull()) {
       return error_message.raw();
     }
-    lib ^= lib.next_registered();
   }
   return String::null();
 }
@@ -5437,16 +5443,17 @@ RawString* Library::CheckForDuplicateDefinition() {
 
 bool Library::IsKeyUsed(intptr_t key) {
   intptr_t lib_key;
+  const GrowableObjectArray& libs = GrowableObjectArray::Handle(
+      Isolate::Current()->object_store()->libraries());
   Library& lib = Library::Handle();
-  lib = Isolate::Current()->object_store()->registered_libraries();
   String& lib_url = String::Handle();
-  while (!lib.IsNull()) {
+  for (int i = 0; i < libs.Length(); i++) {
+    lib ^= libs.At(i);
     lib_url ^= lib.url();
     lib_key = lib_url.Hash();
     if (lib_key == key) {
       return true;
     }
-    lib = lib.next_registered();
   }
   return false;
 }
@@ -5463,11 +5470,27 @@ RawString* Library::PrivateName(const String& name) const {
 }
 
 
+RawLibrary* Library::GetLibrary(intptr_t index) {
+  Isolate* isolate = Isolate::Current();
+  const GrowableObjectArray& libs =
+      GrowableObjectArray::Handle(isolate->object_store()->libraries());
+  ASSERT(!libs.IsNull());
+  if ((0 <= index) && (index < libs.Length())) {
+    Library& lib = Library::Handle();
+    lib ^= libs.At(index);
+    return lib.raw();
+  }
+  return Library::null();
+}
+
+
 void Library::Register() const {
   ASSERT(Library::LookupLibrary(String::Handle(url())) == Library::null());
-  raw_ptr()->next_registered_ =
-      Isolate::Current()->object_store()->registered_libraries();
-  Isolate::Current()->object_store()->set_registered_libraries(*this);
+  ObjectStore* object_store = Isolate::Current()->object_store();
+  GrowableObjectArray& libs =
+      GrowableObjectArray::Handle(object_store->libraries());
+  ASSERT(!libs.IsNull());
+  libs.Add(*this);
 }
 
 
@@ -5667,10 +5690,12 @@ void LibraryPrefix::set_num_libs(intptr_t value) const {
 
 RawError* Library::CompileAll() {
   Error& error = Error::Handle();
-  Library& lib = Library::Handle(
-      Isolate::Current()->object_store()->registered_libraries());
+  const GrowableObjectArray& libs = GrowableObjectArray::Handle(
+      Isolate::Current()->object_store()->libraries());
+  Library& lib = Library::Handle();
   Class& cls = Class::Handle();
-  while (!lib.IsNull()) {
+  for (int i = 0; i < libs.Length(); i++) {
+    lib ^= libs.At(i);
     ClassDictionaryIterator it(lib);
     while (it.HasNext()) {
       cls ^= it.GetNextClass();
@@ -5690,7 +5715,6 @@ RawError* Library::CompileAll() {
         return error.raw();
       }
     }
-    lib = lib.next_registered();
   }
   return error.raw();
 }
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 701138d40af..7dba560fe0a 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -1770,11 +1770,10 @@ class Library : public Object {
 
   void Register() const;
 
-  RawLibrary* next_registered() const { return raw_ptr()->next_registered_; }
-
   RawString* DuplicateDefineErrorString(const String& entry_name,
                                         const Library& conflicting_lib) const;
   static RawLibrary* LookupLibrary(const String& url);
+  static RawLibrary* GetLibrary(intptr_t index);
   static RawString* CheckForDuplicateDefinition();
   static bool IsKeyUsed(intptr_t key);
 
diff --git a/runtime/vm/object_store.cc b/runtime/vm/object_store.cc
index b0b9b283314..e45f92d4539 100644
--- a/runtime/vm/object_store.cc
+++ b/runtime/vm/object_store.cc
@@ -71,8 +71,8 @@ ObjectStore::ObjectStore()
     native_wrappers_library_(Library::null()),
     builtin_library_(Library::null()),
     root_library_(Library::null()),
+    libraries_(GrowableObjectArray::null()),
     import_map_(Array::null()),
-    registered_libraries_(Library::null()),
     pending_classes_(GrowableObjectArray::null()),
     sticky_error_(Error::null()),
     empty_context_(Context::null()),
diff --git a/runtime/vm/object_store.h b/runtime/vm/object_store.h
index 15f1133aa69..8f10ef96d5e 100644
--- a/runtime/vm/object_store.h
+++ b/runtime/vm/object_store.h
@@ -443,17 +443,16 @@ class ObjectStore {
     root_library_ = value.raw();
   }
 
+  RawGrowableObjectArray* libraries() const { return libraries_; }
+  void set_libraries(const GrowableObjectArray& value) {
+    libraries_ = value.raw();
+  }
+
   RawArray* import_map() const { return import_map_; }
   void set_import_map(const Array& value) {
     import_map_ = value.raw();
   }
 
-  // Returns head of list of registered libraries.
-  RawLibrary* registered_libraries() const { return registered_libraries_; }
-  void set_registered_libraries(const Library& value) {
-    registered_libraries_ = value.raw();
-  }
-
   RawGrowableObjectArray* pending_classes() const { return pending_classes_; }
   void set_pending_classes(const GrowableObjectArray& value) {
     ASSERT(!value.IsNull());
@@ -578,8 +577,8 @@ class ObjectStore {
   RawLibrary* native_wrappers_library_;
   RawLibrary* builtin_library_;
   RawLibrary* root_library_;
+  RawGrowableObjectArray* libraries_;
   RawArray* import_map_;
-  RawLibrary* registered_libraries_;
   RawGrowableObjectArray* pending_classes_;
   RawError* sticky_error_;
   RawContext* empty_context_;
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 47299551cf2..4d67bb099d9 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -668,10 +668,9 @@ class RawLibrary : public RawObject {
   RawArray* imports_;            // List of libraries imported without prefix.
   RawArray* imported_into_;      // List of libraries where this library
                                  // is imported into without a prefix.
-  RawLibrary* next_registered_;  // Linked list of registered libraries.
   RawArray* loaded_scripts_;     // Array of scripts loaded in this library.
   RawObject** to() {
-    return reinterpret_cast<RawObject**>(&ptr()->next_registered_);
+    return reinterpret_cast<RawObject**>(&ptr()->loaded_scripts_);
   }
 
   intptr_t num_imports_;         // Number of entries in imports_.