diff --git a/src/Composer/Command/SearchCommand.php b/src/Composer/Command/SearchCommand.php
index 1b3a535a0..e332ac1f8 100644
--- a/src/Composer/Command/SearchCommand.php
+++ b/src/Composer/Command/SearchCommand.php
@@ -27,7 +27,7 @@ use Composer\Factory;
 class SearchCommand extends Command
 {
     protected $matches;
-    protected $lowMatches;
+    protected $lowMatches = array();
     protected $tokens;
     protected $output;
 
diff --git a/src/Composer/Repository/ArrayRepository.php b/src/Composer/Repository/ArrayRepository.php
index 07f648e0f..49ddd99d5 100644
--- a/src/Composer/Repository/ArrayRepository.php
+++ b/src/Composer/Repository/ArrayRepository.php
@@ -118,7 +118,7 @@ class ArrayRepository implements RepositoryInterface
     public function filterPackages($callback, $class = 'Composer\Package\Package')
     {
         foreach ($this->getPackages() as $package) {
-            if (false === $callback($package)) {
+            if (false === call_user_func($callback, $package)) {
                 return false;
             }
         }
diff --git a/src/Composer/Repository/ComposerRepository.php b/src/Composer/Repository/ComposerRepository.php
index 123e08bce..0ea86e5e8 100644
--- a/src/Composer/Repository/ComposerRepository.php
+++ b/src/Composer/Repository/ComposerRepository.php
@@ -135,11 +135,11 @@ class ComposerRepository extends ArrayRepository implements NotifiableRepository
         }
 
         foreach ($this->rawData as $package) {
-            if (false === $callback($package = $this->loader->load($package, $class))) {
+            if (false === call_user_func($callback, $package = $this->loader->load($package, $class))) {
                 return false;
             }
             if ($package->getAlias()) {
-                if (false === $callback($this->createAliasPackage($package))) {
+                if (false === call_user_func($callback, $this->createAliasPackage($package))) {
                     return false;
                 }
             }