diff --git a/src/Plugin.php b/src/Plugin.php
index 1872a7b..4439d40 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -4,7 +4,6 @@
 
 use Composer\Composer;
 use Composer\DependencyResolver\Operation\InstallOperation;
-use Composer\DependencyResolver\Operation\UpdateOperation;
 use Composer\DependencyResolver\Pool;
 use Composer\EventDispatcher\EventDispatcher;
 use Composer\EventDispatcher\EventSubscriberInterface;
@@ -37,6 +36,9 @@ class Plugin implements PluginInterface, EventSubscriberInterface
     /** @var Composer */
     private $composer;
 
+    /** @var string[] */
+    private $installedPackages;
+
     /** @var IOInterface */
     private $io;
 
@@ -58,6 +60,11 @@ public function activate(Composer $composer, IOInterface $io)
     {
         $this->composer = $composer;
         $this->io = $io;
+
+        $installedPackages = $this->composer->getRepositoryManager()->getLocalRepository()->getPackages();
+        foreach ($installedPackages as $package) {
+            $this->installedPackages[$package->getName()] = $package->getPrettyVersion();
+        }
     }
 
     public function onPostPackage(PackageEvent $event)
@@ -145,14 +152,28 @@ private function runInstaller(RootPackageInterface $rootPackage, array $packages
 
     private function promptForPackageVersion($name)
     {
-        $validator = function ($input) {
-            $input = trim($input);
-            return $input ?: false;
-        };
+        // Package is currently installed. Add it to root composer.json
+        if (isset($this->installedPackages[$name])) {
+            $this->io->write(sprintf(
+                'Added package <info>%s</info> to composer.json with constraint <info>%s</info>;'
+                    . ' to upgrade, run <info>composer require %s:VERSION</info>',
+                $name,
+                '^' . $this->installedPackages[$name],
+                $name
+            ));
+
+            return '^' . $this->installedPackages[$name];
+        }
 
         $constraint = $this->io->askAndValidate(
-            sprintf('Enter the version of %s to require (or leave blank to use the latest version): ', $name),
-            $validator
+            sprintf(
+                'Enter the version of <info>%s</info> to require (or leave blank to use the latest version): ',
+                $name
+            ),
+            function ($input) {
+                $input = trim($input);
+                return $input ?: false;
+            }
         );
 
         if ($constraint === false) {
@@ -184,11 +205,11 @@ private function createInstaller(Composer $composer, IOInterface $io, RootPackag
         );
     }
 
-    private function hasPackage($name)
+    private function hasPackage($package)
     {
         $requires = $this->composer->getPackage()->getRequires();
-        foreach ($requires as $link) {
-            if (strtolower($link->getTarget()) === strtolower($name)) {
+        foreach ($requires as $name => $link) {
+            if (strtolower($name) === strtolower($package)) {
                 return true;
             }
         }
diff --git a/test/PluginTest.php b/test/PluginTest.php
index ba3a38e..288a8d3 100644
--- a/test/PluginTest.php
+++ b/test/PluginTest.php
@@ -18,6 +18,7 @@
 use Composer\Package\RootPackageInterface;
 use Composer\Package\Version\VersionSelector;
 use Composer\Repository\RepositoryManager;
+use Composer\Repository\WritableRepositoryInterface;
 use org\bovigo\vfs\vfsStream;
 use PHPUnit\Framework\TestCase;
 use Prophecy\Argument;
@@ -37,11 +38,24 @@ class PluginTest extends TestCase
     /** @var IOInterface|ObjectProphecy */
     private $io;
 
+    /** @var WritableRepositoryInterface */
+    private $localRepository;
+
     protected function setUp()
     {
         parent::setUp();
 
+        $this->localRepository = $this->prophesize(WritableRepositoryInterface::class);
+        $this->localRepository->getPackages()->willReturn([]);
+
+        $repositoryManager = $this->prophesize(RepositoryManager::class);
+        $repositoryManager->getLocalRepository()->willReturn($this->localRepository->reveal());
+
         $this->composer = $this->prophesize(Composer::class);
+        $this->composer->getRepositoryManager()
+            ->willReturn($repositoryManager->reveal())
+            ->shouldBeCalled();
+
         $this->io = $this->prophesize(IOInterface::class);
 
         $this->plugin = new Plugin();
@@ -244,7 +258,8 @@ public function testInstallSingleDependencyOnPackageUpdate()
         $this->composer->getConfig()->willReturn($config->reveal());
 
         $this->io->askAndValidate(
-            'Enter the version of extra-dependency-foo to require (or leave blank to use the latest version): ',
+            'Enter the version of <info>extra-dependency-foo</info> to require'
+                . ' (or leave blank to use the latest version): ',
             Argument::type('callable')
         )->willReturn('17.0.1-dev');
 
@@ -316,7 +331,8 @@ public function testInstallSingleDependencyOnPackageInstall()
         $this->composer->getConfig()->willReturn($config->reveal());
 
         $this->io->askAndValidate(
-            'Enter the version of extra-dependency-foo to require (or leave blank to use the latest version): ',
+            'Enter the version of <info>extra-dependency-foo</info> to require'
+                . ' (or leave blank to use the latest version): ',
             Argument::type('callable')
         )->willReturn('17.0.1-dev');
 
@@ -396,7 +412,8 @@ public function testInstallOneDependenciesWhenOneIsAlreadyInstalled()
         $this->composer->getConfig()->willReturn($config->reveal());
 
         $this->io->askAndValidate(
-            'Enter the version of extra-dependency-foo to require (or leave blank to use the latest version): ',
+            'Enter the version of <info>extra-dependency-foo</info> to require'
+                . ' (or leave blank to use the latest version): ',
             Argument::type('callable')
         )->willReturn('17.0.1-dev');
 
@@ -474,7 +491,8 @@ public function testInstallSingleDependencyAndAutomaticallyChooseLatestVersion()
         $this->composer->getConfig()->willReturn($config->reveal());
 
         $this->io->askAndValidate(
-            'Enter the version of extra-dependency-foo to require (or leave blank to use the latest version): ',
+            'Enter the version of <info>extra-dependency-foo</info> to require'
+                . ' (or leave blank to use the latest version): ',
             Argument::type('callable')
         )->willReturn(false);
 
@@ -500,6 +518,11 @@ public function testInstallSingleDependencyAndAutomaticallyChooseLatestVersion()
         $this->setUpPool();
 
         $this->assertNull($this->plugin->onPostPackage($event->reveal()));
+
+        $json = file_get_contents(vfsStream::url('project/composer.json'));
+        $composer = json_decode($json, true);
+        $this->assertTrue(isset($composer['require']['extra-dependency-foo']));
+        $this->assertSame('13.4.2', $composer['require']['extra-dependency-foo']);
     }
 
     public function testInstallSingleDependencyAndAutomaticallyChooseLatestVersionNotFoundMatchingPackage()
@@ -532,7 +555,8 @@ public function testInstallSingleDependencyAndAutomaticallyChooseLatestVersionNo
         $this->composer->getConfig()->willReturn($config->reveal());
 
         $this->io->askAndValidate(
-            'Enter the version of extra-dependency-foo to require (or leave blank to use the latest version): ',
+            'Enter the version of <info>extra-dependency-foo</info> to require'
+                . ' (or leave blank to use the latest version): ',
             Argument::type('callable')
         )->willReturn(false);
 
@@ -551,6 +575,82 @@ public function testInstallSingleDependencyAndAutomaticallyChooseLatestVersionNo
         $this->plugin->onPostPackage($event->reveal());
     }
 
+    public function testUpdateComposerWithCurrentlyInstalledVersion()
+    {
+        $installedPackage = $this->prophesize(PackageInterface::class);
+        $installedPackage->getName()->willReturn('extra-dependency-foo');
+        $installedPackage->getPrettyVersion()->willReturn('0.5.1');
+
+        $this->localRepository->getPackages()->willReturn([$installedPackage->reveal()]);
+        $this->plugin->activate($this->composer->reveal(), $this->io->reveal());
+
+        /** @var PackageInterface|ObjectProphecy $package */
+        $package = $this->prophesize(PackageInterface::class);
+        $package->getName()->willReturn('some/component');
+        $package->getExtra()->willReturn([
+            'dependency' => [
+                'extra-dependency-foo',
+            ],
+        ]);
+
+        $operation = $this->prophesize(InstallOperation::class);
+        $operation->getPackage()->willReturn($package->reveal());
+
+        $event = $this->prophesize(PackageEvent::class);
+        $event->isDevMode()->willReturn(true);
+        $event->getOperation()->willReturn($operation->reveal());
+
+        $config = $this->prophesize(Config::class);
+        $config->get('sort-packages')->willReturn(true);
+        $config->get(Argument::any())->willReturn(null);
+
+        $rootPackage = $this->prophesize(RootPackageInterface::class);
+        $rootPackage->getRequires()->willReturn([]);
+        $rootPackage->setRequires(Argument::that(function ($arguments) {
+            if (! is_array($arguments)) {
+                return false;
+            }
+
+            if (! isset($arguments['extra-dependency-foo'])) {
+                return false;
+            }
+
+            $argument = $arguments['extra-dependency-foo'];
+
+            if (! $argument instanceof Link) {
+                return false;
+            }
+
+            if ($argument->getTarget() !== 'extra-dependency-foo') {
+                return false;
+            }
+
+            if ($argument->getConstraint()->getPrettyString() !== '^0.5.1') {
+                return false;
+            }
+
+            if ($argument->getDescription() !== 'requires') {
+                return false;
+            }
+
+            return true;
+        }))->shouldBeCalled();
+        $rootPackage->getMinimumStability()->willReturn('stable');
+
+        $this->composer->getPackage()->willReturn($rootPackage);
+        $this->composer->getConfig()->willReturn($config->reveal());
+
+        $this->setUpComposerInstaller(['extra-dependency-foo']);
+        $this->setUpComposerJson();
+
+        $this->assertNull($this->plugin->onPostPackage($event->reveal()));
+
+        $json = file_get_contents(vfsStream::url('project/composer.json'));
+        $composer = json_decode($json, true);
+        $this->assertTrue(isset($composer['require']['extra-dependency-foo']));
+        $this->assertSame('^0.5.1', $composer['require']['extra-dependency-foo']);
+    }
+
     public function testComposerInstallerFactory()
     {
         $r = new ReflectionProperty($this->plugin, 'installerFactory');
@@ -563,9 +663,6 @@ public function testComposerInstallerFactory()
         $this->composer->getDownloadManager()
             ->willReturn($this->prophesize(DownloadManager::class))
             ->shouldBeCalled();
-        $this->composer->getRepositoryManager()
-            ->willReturn($this->prophesize(RepositoryManager::class))
-            ->shouldBeCalled();
         $this->composer->getLocker()
             ->willReturn($this->prophesize(Locker::class))
             ->shouldBeCalled();