diff --git a/src/Composer/Repository/Vcs/GitBitbucketDriver.php b/src/Composer/Repository/Vcs/GitBitbucketDriver.php
index 6a4e242a9..8424ba61a 100644
--- a/src/Composer/Repository/Vcs/GitBitbucketDriver.php
+++ b/src/Composer/Repository/Vcs/GitBitbucketDriver.php
@@ -293,7 +293,7 @@ class GitBitbucketDriver extends VcsDriver
         }
 
         if (null === $this->tags) {
-            $this->tags = array();
+            $tags = array();
             $resource = sprintf(
                 '%s?%s',
                 $this->tagsUrl,
@@ -311,7 +311,7 @@ class GitBitbucketDriver extends VcsDriver
             while ($hasNext) {
                 $tagsData = $this->fetchWithOAuthCredentials($resource)->decodeJson();
                 foreach ($tagsData['values'] as $data) {
-                    $this->tags[$data['name']] = $data['target']['hash'];
+                    $tags[$data['name']] = $data['target']['hash'];
                 }
                 if (empty($tagsData['next'])) {
                     $hasNext = false;
@@ -319,6 +319,8 @@ class GitBitbucketDriver extends VcsDriver
                     $resource = $tagsData['next'];
                 }
             }
+
+            $this->tags = $tags;
         }
 
         return $this->tags;
@@ -334,7 +336,7 @@ class GitBitbucketDriver extends VcsDriver
         }
 
         if (null === $this->branches) {
-            $this->branches = array();
+            $branches = array();
             $resource = sprintf(
                 '%s?%s',
                 $this->branchesUrl,
@@ -352,7 +354,7 @@ class GitBitbucketDriver extends VcsDriver
             while ($hasNext) {
                 $branchData = $this->fetchWithOAuthCredentials($resource)->decodeJson();
                 foreach ($branchData['values'] as $data) {
-                    $this->branches[$data['name']] = $data['target']['hash'];
+                    $branches[$data['name']] = $data['target']['hash'];
                 }
                 if (empty($branchData['next'])) {
                     $hasNext = false;
@@ -360,6 +362,8 @@ class GitBitbucketDriver extends VcsDriver
                     $resource = $branchData['next'];
                 }
             }
+
+            $this->branches = $branches;
         }
 
         return $this->branches;
diff --git a/src/Composer/Repository/Vcs/GitHubDriver.php b/src/Composer/Repository/Vcs/GitHubDriver.php
index f186bb6f5..07daab475 100644
--- a/src/Composer/Repository/Vcs/GitHubDriver.php
+++ b/src/Composer/Repository/Vcs/GitHubDriver.php
@@ -322,18 +322,20 @@ class GitHubDriver extends VcsDriver
             return $this->gitDriver->getTags();
         }
         if (null === $this->tags) {
-            $this->tags = array();
+            $tags = array();
             $resource = $this->getApiUrl() . '/repos/'.$this->owner.'/'.$this->repository.'/tags?per_page=100';
 
             do {
                 $response = $this->getContents($resource);
                 $tagsData = $response->decodeJson();
                 foreach ($tagsData as $tag) {
-                    $this->tags[$tag['name']] = $tag['commit']['sha'];
+                    $tags[$tag['name']] = $tag['commit']['sha'];
                 }
 
                 $resource = $this->getNextPage($response);
             } while ($resource);
+
+            $this->tags = $tags;
         }
 
         return $this->tags;
@@ -348,7 +350,7 @@ class GitHubDriver extends VcsDriver
             return $this->gitDriver->getBranches();
         }
         if (null === $this->branches) {
-            $this->branches = array();
+            $branches = array();
             $resource = $this->getApiUrl() . '/repos/'.$this->owner.'/'.$this->repository.'/git/refs/heads?per_page=100';
 
             do {
@@ -357,12 +359,14 @@ class GitHubDriver extends VcsDriver
                 foreach ($branchData as $branch) {
                     $name = substr($branch['ref'], 11);
                     if ($name !== 'gh-pages') {
-                        $this->branches[$name] = $branch['object']['sha'];
+                        $branches[$name] = $branch['object']['sha'];
                     }
                 }
 
                 $resource = $this->getNextPage($response);
             } while ($resource);
+
+            $this->branches = $branches;
         }
 
         return $this->branches;
diff --git a/src/Composer/Repository/Vcs/SvnDriver.php b/src/Composer/Repository/Vcs/SvnDriver.php
index f375c900a..6380ea387 100644
--- a/src/Composer/Repository/Vcs/SvnDriver.php
+++ b/src/Composer/Repository/Vcs/SvnDriver.php
@@ -222,7 +222,7 @@ class SvnDriver extends VcsDriver
     public function getTags()
     {
         if (null === $this->tags) {
-            $this->tags = array();
+            $tags = array();
 
             if ($this->tagsPath !== false) {
                 $output = $this->execute('svn ls --verbose', $this->baseUrl . '/' . $this->tagsPath);
@@ -231,7 +231,7 @@ class SvnDriver extends VcsDriver
                         $line = trim($line);
                         if ($line && preg_match('{^\s*(\S+).*?(\S+)\s*$}', $line, $match)) {
                             if (isset($match[1], $match[2]) && $match[2] !== './') {
-                                $this->tags[rtrim($match[2], '/')] = $this->buildIdentifier(
+                                $tags[rtrim($match[2], '/')] = $this->buildIdentifier(
                                     '/' . $this->tagsPath . '/' . $match[2],
                                     $match[1]
                                 );
@@ -240,6 +240,8 @@ class SvnDriver extends VcsDriver
                     }
                 }
             }
+
+            $this->tags = $tags;
         }
 
         return $this->tags;
@@ -251,7 +253,7 @@ class SvnDriver extends VcsDriver
     public function getBranches()
     {
         if (null === $this->branches) {
-            $this->branches = array();
+            $branches = array();
 
             if (false === $this->trunkPath) {
                 $trunkParent = $this->baseUrl . '/';
@@ -265,11 +267,11 @@ class SvnDriver extends VcsDriver
                     $line = trim($line);
                     if ($line && preg_match('{^\s*(\S+).*?(\S+)\s*$}', $line, $match)) {
                         if (isset($match[1], $match[2]) && $match[2] === './') {
-                            $this->branches['trunk'] = $this->buildIdentifier(
+                            $branches['trunk'] = $this->buildIdentifier(
                                 '/' . $this->trunkPath,
                                 $match[1]
                             );
-                            $this->rootIdentifier = $this->branches['trunk'];
+                            $this->rootIdentifier = $branches['trunk'];
                             break;
                         }
                     }
@@ -284,7 +286,7 @@ class SvnDriver extends VcsDriver
                         $line = trim($line);
                         if ($line && preg_match('{^\s*(\S+).*?(\S+)\s*$}', $line, $match)) {
                             if (isset($match[1], $match[2]) && $match[2] !== './') {
-                                $this->branches[rtrim($match[2], '/')] = $this->buildIdentifier(
+                                $branches[rtrim($match[2], '/')] = $this->buildIdentifier(
                                     '/' . $this->branchesPath . '/' . $match[2],
                                     $match[1]
                                 );
@@ -293,6 +295,8 @@ class SvnDriver extends VcsDriver
                     }
                 }
             }
+
+            $this->branches = $branches;
         }
 
         return $this->branches;
diff --git a/src/Composer/Repository/VcsRepository.php b/src/Composer/Repository/VcsRepository.php
index b6b0f7cc2..2281f1c76 100644
--- a/src/Composer/Repository/VcsRepository.php
+++ b/src/Composer/Repository/VcsRepository.php
@@ -212,6 +212,10 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
                 $this->packageName = !empty($data['name']) ? $data['name'] : null;
             }
         } catch (\Exception $e) {
+            if ($e instanceof TransportException && $this->shouldRethrowTransportException($e)) {
+                throw $e;
+            }
+
             if ($isVeryVerbose) {
                 $this->io->writeError('<error>Skipped parsing '.$driver->getRootIdentifier().', '.$e->getMessage().'</error>');
             }
@@ -303,7 +307,7 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
                     if ($e->getCode() === 404) {
                         $this->emptyReferences[] = $identifier;
                     }
-                    if (in_array($e->getCode(), array(401, 403, 429), true)) {
+                    if ($this->shouldRethrowTransportException($e)) {
                         throw $e;
                     }
                 }
@@ -392,7 +396,7 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
                 if ($e->getCode() === 404) {
                     $this->emptyReferences[] = $identifier;
                 }
-                if (in_array($e->getCode(), array(401, 403, 429), true)) {
+                if ($this->shouldRethrowTransportException($e)) {
                     throw $e;
                 }
                 if ($isVeryVerbose) {
@@ -531,4 +535,12 @@ class VcsRepository extends ArrayRepository implements ConfigurableRepositoryInt
 
         return null;
     }
+
+    /**
+     * @return bool
+     */
+    private function shouldRethrowTransportException(TransportException $e)
+    {
+        return in_array($e->getCode(), array(401, 403, 429), true) || $e->getCode() >= 500;
+    }
 }