diff --git a/src/Composer/Installer/PluginInstaller.php b/src/Composer/Installer/PluginInstaller.php
index 62a16fc62..a52e1937e 100644
--- a/src/Composer/Installer/PluginInstaller.php
+++ b/src/Composer/Installer/PluginInstaller.php
@@ -70,7 +70,7 @@ class PluginInstaller extends LibraryInstaller
             $this->composer->getPluginManager()->registerPackage($package, true);
         } catch (\Exception $e) {
             // Rollback installation
-            $this->io->writeError('Plugin installation failed, rolling back');
+            $this->io->writeError('Plugin initialization failed, uninstalling plugin');
             parent::uninstall($repo, $package);
             throw $e;
         }
@@ -81,12 +81,22 @@ class PluginInstaller extends LibraryInstaller
      */
     public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target)
     {
-        $extra = $target->getExtra();
-        if (empty($extra['class'])) {
-            throw new \UnexpectedValueException('Error while installing '.$target->getPrettyName().', composer-plugin packages should have a class defined in their extra key to be usable.');
-        }
-
         parent::update($repo, $initial, $target);
-        $this->composer->getPluginManager()->registerPackage($target, true);
+
+        try {
+            $this->composer->getPluginManager()->deactivatePackage($initial, true);
+            $this->composer->getPluginManager()->registerPackage($target, true);
+        } catch (\Exception $e) {
+            // Rollback installation
+            $this->io->writeError('Plugin initialization failed, uninstalling plugin');
+            parent::uninstall($repo, $target);
+            throw $e;
+        }
+    }
+
+    public function uninstall(InstalledRepositoryInterface $repo, PackageInterface $package)
+    {
+        $this->composer->getPluginManager()->uninstallPackage($package, true);
+        parent::uninstall($repo, $package);
     }
 }
diff --git a/src/Composer/Plugin/PluginInterface.php b/src/Composer/Plugin/PluginInterface.php
index 5158b66f6..27b8c9754 100644
--- a/src/Composer/Plugin/PluginInterface.php
+++ b/src/Composer/Plugin/PluginInterface.php
@@ -36,4 +36,22 @@ interface PluginInterface
      * @param IOInterface $io
      */
     public function activate(Composer $composer, IOInterface $io);
+
+    /**
+     * Remove any hooks from Composer
+     *
+     * @param Composer    $composer
+     * @param IOInterface $io
+     */
+    public function deactivate(Composer $composer, IOInterface $io);
+
+    /**
+     * Prepare the plugin to be uninstalled
+     *
+     * This will be called after deactivate
+     *
+     * @param Composer    $composer
+     * @param IOInterface $io
+     */
+    public function uninstall(Composer $composer, IOInterface $io);
 }
diff --git a/src/Composer/Plugin/PluginManager.php b/src/Composer/Plugin/PluginManager.php
index 786d846c5..7408359bd 100644
--- a/src/Composer/Plugin/PluginManager.php
+++ b/src/Composer/Plugin/PluginManager.php
@@ -144,7 +144,7 @@ class PluginManager
 
         $oldInstallerPlugin = ($package->getType() === 'composer-installer');
 
-        if (in_array($package->getName(), $this->registeredPlugins)) {
+        if (isset($this->registeredPlugins[$package->getName()])) {
             return;
         }
 
@@ -200,16 +200,82 @@ class PluginManager
             if ($oldInstallerPlugin) {
                 $installer = new $class($this->io, $this->composer);
                 $this->composer->getInstallationManager()->addInstaller($installer);
+                $this->registeredPlugins[$package->getName()] = $installer;
             } elseif (class_exists($class)) {
                 $plugin = new $class();
                 $this->addPlugin($plugin);
-                $this->registeredPlugins[] = $package->getName();
+                $this->registeredPlugins[$package->getName()] = $plugin;
             } elseif ($failOnMissingClasses) {
                 throw new \UnexpectedValueException('Plugin '.$package->getName().' could not be initialized, class not found: '.$class);
             }
         }
     }
 
+    /**
+     * Deactivates a plugin package
+     *
+     * If it's of type composer-installer it is unregistered from the installers
+     * instead for BC
+     *
+     * @param PackageInterface $package
+     *
+     * @throws \UnexpectedValueException
+     */
+    public function deactivatePackage(PackageInterface $package)
+    {
+        if ($this->disablePlugins) {
+            return;
+        }
+
+        $oldInstallerPlugin = ($package->getType() === 'composer-installer');
+
+        if (!isset($this->registeredPlugins[$package->getName()])) {
+            return;
+        }
+
+        if ($oldInstallerPlugin) {
+            $installer = $this->registeredPlugins[$package->getName()];
+            unset($this->registeredPlugins[$package->getName()]);
+            $this->composer->getInstallationManager()->removeInstaller($installer);
+        } else {
+            $plugin = $this->registeredPlugins[$package->getName()];
+            unset($this->registeredPlugins[$package->getName()]);
+            $this->removePlugin($plugin);
+        }
+    }
+
+    /**
+     * Uninstall a plugin package
+     *
+     * If it's of type composer-installer it is unregistered from the installers
+     * instead for BC
+     *
+     * @param PackageInterface $package
+     *
+     * @throws \UnexpectedValueException
+     */
+    public function uninstallPackage(PackageInterface $package)
+    {
+        if ($this->disablePlugins) {
+            return;
+        }
+
+        $oldInstallerPlugin = ($package->getType() === 'composer-installer');
+
+        if (!isset($this->registeredPlugins[$package->getName()])) {
+            return;
+        }
+
+        if ($oldInstallerPlugin) {
+            $this->deactivatePackage($package);
+        } else {
+            $plugin = $this->registeredPlugins[$package->getName()];
+            unset($this->registeredPlugins[$package->getName()]);
+            $this->removePlugin($plugin);
+            $this->uninstallPlugin($plugin);
+        }
+    }
+
     /**
      * Returns the version of the internal composer-plugin-api package.
      *
@@ -240,6 +306,44 @@ class PluginManager
         }
     }
 
+    /**
+     * Removes a plugin, deactivates it and removes any listener the plugin has set on the plugin instance
+     *
+     * Ideally plugin packages should be deactivated via deactivatePackage, but if you use Composer
+     * programmatically and want to deregister a plugin class directly this is a valid way
+     * to do it.
+     *
+     * @param PluginInterface $plugin plugin instance
+     */
+    public function removePlugin(PluginInterface $plugin)
+    {
+        $index = array_search($plugin, $this->plugins, true);
+        if ($index === false) {
+            return;
+        }
+
+        $this->io->writeError('Unloading plugin '.get_class($plugin), true, IOInterface::DEBUG);
+        unset($this->plugins[$index]);
+        $plugin->deactivate($this->composer, $this->io);
+
+        $this->composer->getEventDispatcher()->removeListener($plugin);
+    }
+
+    /**
+     * Notifies a plugin it is being uninstalled and should clean up
+     *
+     * Ideally plugin packages should be uninstalled via uninstallPackage, but if you use Composer
+     * programmatically and want to deregister a plugin class directly this is a valid way
+     * to do it.
+     *
+     * @param PluginInterface $plugin plugin instance
+     */
+    public function uninstallPlugin(PluginInterface $plugin)
+    {
+        $this->io->writeError('Uninstalling plugin '.get_class($plugin), true, IOInterface::DEBUG);
+        $plugin->uninstall($this->composer, $this->io);
+    }
+
     /**
      * Load all plugins and installers from a repository
      *
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v1/Installer/Plugin.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v1/Installer/Plugin.php
index f80acd325..c757d4b09 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v1/Installer/Plugin.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v1/Installer/Plugin.php
@@ -12,5 +12,16 @@ class Plugin implements PluginInterface
 
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v1');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v1');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v1');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v2/Installer/Plugin2.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v2/Installer/Plugin2.php
index db5a4462e..32090b66d 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v2/Installer/Plugin2.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v2/Installer/Plugin2.php
@@ -12,5 +12,16 @@ class Plugin2 implements PluginInterface
 
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v2');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v2');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v2');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v3/Installer/Plugin2.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v3/Installer/Plugin2.php
index 861c1679b..034388162 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v3/Installer/Plugin2.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v3/Installer/Plugin2.php
@@ -12,5 +12,16 @@ class Plugin2 implements PluginInterface
 
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v3');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v3');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v3');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin1.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin1.php
index 93bcabc98..2eaee6a3f 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin1.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin1.php
@@ -13,5 +13,16 @@ class Plugin1 implements PluginInterface
 
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v4-plugin1');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v4-plugin1');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v4-plugin1');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin2.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin2.php
index d946deb89..3c5311a82 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin2.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin2.php
@@ -13,5 +13,16 @@ class Plugin2 implements PluginInterface
 
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v4-plugin2');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v4-plugin2');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v4-plugin2');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v5/Installer/Plugin5.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v5/Installer/Plugin5.php
index a2ac37bc5..fb9f08a6d 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v5/Installer/Plugin5.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v5/Installer/Plugin5.php
@@ -10,5 +10,16 @@ class Plugin5 implements PluginInterface
 {
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v5');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v5');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v5');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v6/Installer/Plugin6.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v6/Installer/Plugin6.php
index e46c0fcb0..acce1f972 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v6/Installer/Plugin6.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v6/Installer/Plugin6.php
@@ -10,5 +10,16 @@ class Plugin6 implements PluginInterface
 {
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v6');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v6');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v6');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v7/Installer/Plugin7.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v7/Installer/Plugin7.php
index 5560a6047..84734ce3b 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v7/Installer/Plugin7.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v7/Installer/Plugin7.php
@@ -10,5 +10,16 @@ class Plugin7 implements PluginInterface
 {
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v7');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v7');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v7');
     }
 }
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v8/Installer/Plugin8.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v8/Installer/Plugin8.php
index 7e9a0aab1..4534e13ef 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v8/Installer/Plugin8.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v8/Installer/Plugin8.php
@@ -13,6 +13,17 @@ class Plugin8 implements PluginInterface, Capable
 
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v8');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v8');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v8');
     }
 
     public function getCapabilities()
diff --git a/tests/Composer/Test/Plugin/Fixtures/plugin-v9/Installer/Plugin.php b/tests/Composer/Test/Plugin/Fixtures/plugin-v9/Installer/Plugin.php
index 74e1beb8b..870f11cd1 100644
--- a/tests/Composer/Test/Plugin/Fixtures/plugin-v9/Installer/Plugin.php
+++ b/tests/Composer/Test/Plugin/Fixtures/plugin-v9/Installer/Plugin.php
@@ -14,5 +14,16 @@ class Plugin implements PluginInterface
 
     public function activate(Composer $composer, IOInterface $io)
     {
+        $io->write('activate v9');
+    }
+
+    public function deactivate(Composer $composer, IOInterface $io)
+    {
+        $io->write('deactivate v9');
+    }
+
+    public function uninstall(Composer $composer, IOInterface $io)
+    {
+        $io->write('uninstall v9');
     }
 }
diff --git a/tests/Composer/Test/Plugin/PluginInstallerTest.php b/tests/Composer/Test/Plugin/PluginInstallerTest.php
index 633c5ab18..bd83ce16f 100644
--- a/tests/Composer/Test/Plugin/PluginInstallerTest.php
+++ b/tests/Composer/Test/Plugin/PluginInstallerTest.php
@@ -19,6 +19,9 @@ use Composer\Package\CompletePackage;
 use Composer\Package\Loader\JsonLoader;
 use Composer\Package\Loader\ArrayLoader;
 use Composer\Plugin\PluginManager;
+use Symfony\Component\Console\Output\OutputInterface;
+use Composer\IO\BufferIO;
+use Composer\EventDispatcher\EventDispatcher;
 use Composer\Autoload\AutoloadGenerator;
 use Composer\Test\TestCase;
 use Composer\Util\Filesystem;
@@ -96,7 +99,7 @@ class PluginInstallerTest extends TestCase
                 return __DIR__.'/Fixtures/'.$package->getPrettyName();
             }));
 
-        $this->io = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
+        $this->io = new BufferIO();
 
         $dispatcher = $this->getMockBuilder('Composer\EventDispatcher\EventDispatcher')->disableOriginalConstructor()->getMock();
         $this->autoloadGenerator = new AutoloadGenerator($dispatcher);
@@ -108,6 +111,7 @@ class PluginInstallerTest extends TestCase
         $this->composer->setRepositoryManager($rm);
         $this->composer->setInstallationManager($im);
         $this->composer->setAutoloadGenerator($this->autoloadGenerator);
+        $this->composer->setEventDispatcher(new EventDispatcher($this->composer, $this->io));
 
         $this->pm = new PluginManager($this->io, $this->composer);
         $this->composer->setPluginManager($this->pm);
@@ -140,6 +144,7 @@ class PluginInstallerTest extends TestCase
 
         $plugins = $this->pm->getPlugins();
         $this->assertEquals('installer-v1', $plugins[0]->version);
+        $this->assertEquals('activate v1'.PHP_EOL, $this->io->getOutput());
     }
 
     public function testInstallMultiplePlugins()
@@ -158,6 +163,7 @@ class PluginInstallerTest extends TestCase
         $this->assertEquals('installer-v4', $plugins[0]->version);
         $this->assertEquals('plugin2', $plugins[1]->name);
         $this->assertEquals('installer-v4', $plugins[1]->version);
+        $this->assertEquals('activate v4-plugin1'.PHP_EOL.'activate v4-plugin2'.PHP_EOL, $this->io->getOutput());
     }
 
     public function testUpgradeWithNewClassName()
@@ -176,7 +182,29 @@ class PluginInstallerTest extends TestCase
         $installer->update($this->repository, $this->packages[0], $this->packages[1]);
 
         $plugins = $this->pm->getPlugins();
+        $this->assertCount(1, $plugins);
         $this->assertEquals('installer-v2', $plugins[1]->version);
+        $this->assertEquals('activate v1'.PHP_EOL.'deactivate v1'.PHP_EOL.'activate v2'.PHP_EOL, $this->io->getOutput());
+    }
+
+    public function testUninstall()
+    {
+        $this->repository
+            ->expects($this->once())
+            ->method('getPackages')
+            ->will($this->returnValue(array($this->packages[0])));
+        $this->repository
+            ->expects($this->exactly(1))
+            ->method('hasPackage')
+            ->will($this->onConsecutiveCalls(true, false));
+        $installer = new PluginInstaller($this->io, $this->composer);
+        $this->pm->loadInstalledPlugins();
+
+        $installer->uninstall($this->repository, $this->packages[0]);
+
+        $plugins = $this->pm->getPlugins();
+        $this->assertCount(0, $plugins);
+        $this->assertEquals('activate v1'.PHP_EOL.'deactivate v1'.PHP_EOL.'uninstall v1'.PHP_EOL, $this->io->getOutput());
     }
 
     public function testUpgradeWithSameClassName()
@@ -196,6 +224,7 @@ class PluginInstallerTest extends TestCase
 
         $plugins = $this->pm->getPlugins();
         $this->assertEquals('installer-v3', $plugins[1]->version);
+        $this->assertEquals('activate v2'.PHP_EOL.'deactivate v2'.PHP_EOL.'activate v3'.PHP_EOL, $this->io->getOutput());
     }
 
     public function testRegisterPluginOnlyOneTime()
@@ -213,6 +242,7 @@ class PluginInstallerTest extends TestCase
         $plugins = $this->pm->getPlugins();
         $this->assertCount(1, $plugins);
         $this->assertEquals('installer-v1', $plugins[0]->version);
+        $this->assertEquals('activate v1'.PHP_EOL, $this->io->getOutput());
     }
 
     /**