diff --git a/src/Composer/DependencyResolver/ArrayRepository.php b/src/Composer/DependencyResolver/ArrayRepository.php
index 7b662b77d..716fb27ed 100644
--- a/src/Composer/DependencyResolver/ArrayRepository.php
+++ b/src/Composer/DependencyResolver/ArrayRepository.php
@@ -12,6 +12,8 @@
 
 namespace Composer\DependencyResolver;
 
+use Composer\Package\PackageInterface;
+
 /**
  * A repository implementation that simply stores packages in an array
  *
@@ -24,11 +26,12 @@ class ArrayRepository implements RepositoryInterface
     /**
      * Adds a new package to the repository
      *
-     * @param Package $package
+     * @param PackageInterface $package
      */
-    public function addPackage(Package $package)
+    public function addPackage(PackageInterface $package)
     {
-        $this->packages[$package->getId()] = $package;
+        $package->setRepository($this);
+        $this->packages[] = $package;
     }
 
     /**
@@ -41,16 +44,6 @@ class ArrayRepository implements RepositoryInterface
         return $this->packages;
     }
 
-    /**
-     * Checks if a package is contained in this repository
-     *
-     * @return bool
-     */
-    public function contains(Package $package)
-    {
-        return isset($this->packages[$package->getId()]);
-    }
-
     /**
      * Returns the number of packages in this repository
      *
diff --git a/src/Composer/DependencyResolver/RepositoryInterface.php b/src/Composer/DependencyResolver/RepositoryInterface.php
index 10f9c2c3b..5a054a1a8 100644
--- a/src/Composer/DependencyResolver/RepositoryInterface.php
+++ b/src/Composer/DependencyResolver/RepositoryInterface.php
@@ -18,5 +18,4 @@ namespace Composer\DependencyResolver;
 interface RepositoryInterface extends \Countable
 {
     function getPackages();
-    function contains(Package $package);
 }
diff --git a/src/Composer/DependencyResolver/Solver.php b/src/Composer/DependencyResolver/Solver.php
index fd3d6948f..b10cfa16e 100644
--- a/src/Composer/DependencyResolver/Solver.php
+++ b/src/Composer/DependencyResolver/Solver.php
@@ -255,7 +255,7 @@ class Solver
             $this->addedMap[$package->getId()] = true;
 
             $dontFix = 0;
-            if ($this->installed->contains($package) && !isset($this->fixMap[$package->getId()])) {
+            if ($this->installed === $package->getRepository() && !isset($this->fixMap[$package->getId()])) {
                 $dontFix = 1;
             }
 
@@ -274,7 +274,7 @@ class Solver
                 if ($dontFix) {
                     $foundInstalled = false;
                     foreach ($possibleRequires as $require) {
-                        if ($this->installed->contains($require)) {
+                        if ($this->installed === $require->getRepository()) {
                             $foundInstalled = true;
                             break;
                         }
@@ -297,7 +297,7 @@ class Solver
                 $possibleConflicts = $this->pool->whatProvides($relation->getToPackageName(), $relation->getConstraint());
 
                 foreach ($possibleConflicts as $conflict) {
-                    if ($dontfix && $this->installed->contains($conflict)) {
+                    if ($dontfix && $this->installed === $conflict->getRepository()) {
                         continue;
                     }
 
@@ -457,12 +457,12 @@ class Solver
             foreach ($job['packages'] as $package) {
                 switch ($job['cmd']) {
                     case 'fix':
-                        if ($this->installed->contains($package)) {
+                        if ($this->installed === $package->getRepository()) {
                             $this->fixMap[$package->getId()] = true;
                         }
                         break;
                     case 'update':
-                        if ($this->installed->contains($package)) {
+                        if ($this->installed === $package->getRepository()) {
                             $this->updateMap[$package->getId()] = true;
                         }
                         break;
@@ -547,7 +547,7 @@ class Solver
                     break;
                 case 'lock':
                     foreach ($job['packages'] as $package) {
-                        if ($this->installed->contains($package)) {
+                        if ($this->installed === $package->getRepository()) {
                             $rule = $this->createInstallRule($package, self::RULE_JOB_LOCK);
                         } else {
                             $rule = $this->createRemoveRule($package, self::RULE_JOB_LOCK);
@@ -762,7 +762,7 @@ class Solver
         $minimizationsteps = 0;
         $installedPos = 0;
 
-        $this->installedPackages = array_values($this->installed->getPackages());
+        $this->installedPackages = $this->installed->getPackages();
 
         while (true) {
 
@@ -798,7 +798,7 @@ class Solver
                             if (count($this->installed) != count($this->updateMap)) {
                                 $prunedQueue = array();
                                 foreach ($decisionQueue as $literal) {
-                                    if ($this->installed->contains($literal->getPackage())) {
+                                    if ($this->installed === $literal->getPackage()->getRepository()) {
                                         $prunedQueue[] = $literal;
                                         if (isset($this->updateMap[$literal->getPackageId()])) {
                                             $prunedQueue = $decisionQueue;
diff --git a/src/Composer/Package/BasePackage.php b/src/Composer/Package/BasePackage.php
index 54dbd5748..752392eb7 100644
--- a/src/Composer/Package/BasePackage.php
+++ b/src/Composer/Package/BasePackage.php
@@ -13,6 +13,7 @@
 namespace Composer\Package;
 
 use Composer\DependencyResolver\RelationConstraint\RelationConstraintInterface;
+use Composer\DependencyResolver\RepositoryInterface;
 
 /**
  * Base class for packages providing name storage and default match implementation
@@ -22,6 +23,7 @@ use Composer\DependencyResolver\RelationConstraint\RelationConstraintInterface;
 abstract class BasePackage implements PackageInterface
 {
     protected $name;
+    protected $repository;
 
     /**
      * All descendents' constructors should call this parent constructor
@@ -97,6 +99,19 @@ abstract class BasePackage implements PackageInterface
         return false;
     }
 
+    public function getRepository()
+    {
+        return $this->repository;
+    }
+
+    public function setRepository(RepositoryInterface $repository)
+    {
+        if ($this->repository) {
+            throw new \LogicException('A package can only be added to one repository');
+        }
+        $this->repository = $repository;
+    }
+
     /**
      * Converts the package into a readable and unique string
      *
diff --git a/src/Composer/Package/PackageInterface.php b/src/Composer/Package/PackageInterface.php
index 08c1eb39d..4db93316c 100644
--- a/src/Composer/Package/PackageInterface.php
+++ b/src/Composer/Package/PackageInterface.php
@@ -13,6 +13,7 @@
 namespace Composer\Package;
 
 use Composer\DependencyResolver\RelationConstraint\RelationConstraintInterface;
+use Composer\DependencyResolver\RepositoryInterface;
 
 /**
  * @author Nils Adermann <naderman@naderman.de>
@@ -136,6 +137,20 @@ interface PackageInterface
      */
     function getSuggests();
 
+    /**
+     * Stores a reference to the repository that owns the package
+     *
+     * @param RepositoryInterface $repository
+     */
+    function setRepository(RepositoryInterface $repository);
+
+    /**
+     * Returns a reference to the repository that owns the package
+     *
+     * @return RepositoryInterface
+     */
+    function getRepository();
+
     /**
      * Converts the package into a readable and unique string
      *