diff --git a/src/Composer/Repository/InstalledRepositoryInterface.php b/src/Composer/Repository/InstalledRepositoryInterface.php
index de71d23c6..7b9ddaeae 100644
--- a/src/Composer/Repository/InstalledRepositoryInterface.php
+++ b/src/Composer/Repository/InstalledRepositoryInterface.php
@@ -21,6 +21,6 @@ use Composer\Package\PackageInterface;
  *
  * @author Jordi Boggiano <j.boggiano@seld.be>
  */
-interface InstalledRepositoryInterface
+interface InstalledRepositoryInterface extends WritableRepositoryInterface
 {
 }
diff --git a/tests/Composer/Test/Installer/Fixtures/installer-v1/Installer/Custom.php b/tests/Composer/Test/Installer/Fixtures/installer-v1/Installer/Custom.php
index cfda3c3d3..bfad4a88a 100644
--- a/tests/Composer/Test/Installer/Fixtures/installer-v1/Installer/Custom.php
+++ b/tests/Composer/Test/Installer/Fixtures/installer-v1/Installer/Custom.php
@@ -4,16 +4,16 @@ namespace Installer;
 
 use Composer\Installer\InstallerInterface;
 use Composer\Package\PackageInterface;
-use Composer\Repository\WritableRepositoryInterface;
+use Composer\Repository\InstalledRepositoryInterface;
 
 class Custom implements InstallerInterface
 {
     public $version = 'installer-v1';
 
     public function supports($packageType) {}
-    public function isInstalled(WritableRepositoryInterface $repo, PackageInterface $package) {}
-    public function install(WritableRepositoryInterface $repo, PackageInterface $package) {}
-    public function update(WritableRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target) {}
-    public function uninstall(WritableRepositoryInterface $repo, PackageInterface $package) {}
+    public function isInstalled(InstalledRepositoryInterface $repo, PackageInterface $package) {}
+    public function install(InstalledRepositoryInterface $repo, PackageInterface $package) {}
+    public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target) {}
+    public function uninstall(InstalledRepositoryInterface $repo, PackageInterface $package) {}
     public function getInstallPath(PackageInterface $package) {}
 }
diff --git a/tests/Composer/Test/Installer/Fixtures/installer-v2/Installer/Custom2.php b/tests/Composer/Test/Installer/Fixtures/installer-v2/Installer/Custom2.php
index 52f46371b..f7f5b9108 100644
--- a/tests/Composer/Test/Installer/Fixtures/installer-v2/Installer/Custom2.php
+++ b/tests/Composer/Test/Installer/Fixtures/installer-v2/Installer/Custom2.php
@@ -4,16 +4,16 @@ namespace Installer;
 
 use Composer\Installer\InstallerInterface;
 use Composer\Package\PackageInterface;
-use Composer\Repository\WritableRepositoryInterface;
+use Composer\Repository\InstalledRepositoryInterface;
 
 class Custom2 implements InstallerInterface
 {
     public $version = 'installer-v2';
 
     public function supports($packageType) {}
-    public function isInstalled(WritableRepositoryInterface $repo, PackageInterface $package) {}
-    public function install(WritableRepositoryInterface $repo, PackageInterface $package) {}
-    public function update(WritableRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target) {}
-    public function uninstall(WritableRepositoryInterface $repo, PackageInterface $package) {}
+    public function isInstalled(InstalledRepositoryInterface $repo, PackageInterface $package) {}
+    public function install(InstalledRepositoryInterface $repo, PackageInterface $package) {}
+    public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target) {}
+    public function uninstall(InstalledRepositoryInterface $repo, PackageInterface $package) {}
     public function getInstallPath(PackageInterface $package) {}
 }
diff --git a/tests/Composer/Test/Installer/Fixtures/installer-v3/Installer/Custom2.php b/tests/Composer/Test/Installer/Fixtures/installer-v3/Installer/Custom2.php
index ca8ad7897..6cc952765 100644
--- a/tests/Composer/Test/Installer/Fixtures/installer-v3/Installer/Custom2.php
+++ b/tests/Composer/Test/Installer/Fixtures/installer-v3/Installer/Custom2.php
@@ -4,16 +4,16 @@ namespace Installer;
 
 use Composer\Installer\InstallerInterface;
 use Composer\Package\PackageInterface;
-use Composer\Repository\WritableRepositoryInterface;
+use Composer\Repository\InstalledRepositoryInterface;
 
 class Custom2 implements InstallerInterface
 {
     public $version = 'installer-v3';
 
     public function supports($packageType) {}
-    public function isInstalled(WritableRepositoryInterface $repo, PackageInterface $package) {}
-    public function install(WritableRepositoryInterface $repo, PackageInterface $package) {}
-    public function update(WritableRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target) {}
-    public function uninstall(WritableRepositoryInterface $repo, PackageInterface $package) {}
+    public function isInstalled(InstalledRepositoryInterface $repo, PackageInterface $package) {}
+    public function install(InstalledRepositoryInterface $repo, PackageInterface $package) {}
+    public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target) {}
+    public function uninstall(InstalledRepositoryInterface $repo, PackageInterface $package) {}
     public function getInstallPath(PackageInterface $package) {}
 }
diff --git a/tests/Composer/Test/Installer/InstallationManagerTest.php b/tests/Composer/Test/Installer/InstallationManagerTest.php
index a657ba948..5b404939e 100644
--- a/tests/Composer/Test/Installer/InstallationManagerTest.php
+++ b/tests/Composer/Test/Installer/InstallationManagerTest.php
@@ -21,7 +21,7 @@ class InstallationManagerTest extends \PHPUnit_Framework_TestCase
 {
     public function setUp()
     {
-        $this->repository = $this->getMock('Composer\Repository\WritableRepositoryInterface');
+        $this->repository = $this->getMock('Composer\Repository\InstalledRepositoryInterface');
     }
 
     public function testVendorDirOutsideTheWorkingDir()
diff --git a/tests/Composer/Test/Installer/InstallerInstallerTest.php b/tests/Composer/Test/Installer/InstallerInstallerTest.php
index 2c107c32c..8fd2a7ad2 100644
--- a/tests/Composer/Test/Installer/InstallerInstallerTest.php
+++ b/tests/Composer/Test/Installer/InstallerInstallerTest.php
@@ -34,7 +34,7 @@ class InstallerInstallerTest extends \PHPUnit_Framework_TestCase
             ->disableOriginalConstructor()
             ->getMock();
 
-        $this->repository = $this->getMock('Composer\Repository\WritableRepositoryInterface');
+        $this->repository = $this->getMock('Composer\Repository\InstalledRepositoryInterface');
 
         $this->io = $this->getMock('Composer\IO\IOInterface');
     }
diff --git a/tests/Composer/Test/Installer/LibraryInstallerTest.php b/tests/Composer/Test/Installer/LibraryInstallerTest.php
index 7983cf2a2..3edc8a477 100644
--- a/tests/Composer/Test/Installer/LibraryInstallerTest.php
+++ b/tests/Composer/Test/Installer/LibraryInstallerTest.php
@@ -40,7 +40,7 @@ class LibraryInstallerTest extends TestCase
             ->disableOriginalConstructor()
             ->getMock();
 
-        $this->repository = $this->getMock('Composer\Repository\WritableRepositoryInterface');
+        $this->repository = $this->getMock('Composer\Repository\InstalledRepositoryInterface');
 
         $this->io = $this->getMock('Composer\IO\IOInterface');
     }
diff --git a/tests/Composer/Test/Installer/MetapackageInstallerTest.php b/tests/Composer/Test/Installer/MetapackageInstallerTest.php
index 45d1ff605..1aa3d3e66 100644
--- a/tests/Composer/Test/Installer/MetapackageInstallerTest.php
+++ b/tests/Composer/Test/Installer/MetapackageInstallerTest.php
@@ -22,7 +22,7 @@ class MetapackageInstallerTest extends \PHPUnit_Framework_TestCase
 
     protected function setUp()
     {
-        $this->repository = $this->getMock('Composer\Repository\WritableRepositoryInterface');
+        $this->repository = $this->getMock('Composer\Repository\InstalledRepositoryInterface');
 
         $this->io = $this->getMock('Composer\IO\IOInterface');