diff --git a/src/Composer/Repository/ArtifactRepository.php b/src/Composer/Repository/ArtifactRepository.php
index a0acb7a61..f8b068218 100644
--- a/src/Composer/Repository/ArtifactRepository.php
+++ b/src/Composer/Repository/ArtifactRepository.php
@@ -88,7 +88,12 @@ class ArtifactRepository extends ArrayRepository implements ConfigurableReposito
 
     private function getComposerInformation(\SplFileInfo $file)
     {
-        $json = Zip::getComposerJson($file->getPathname());
+        $json = null;
+        try {
+            $json = Zip::getComposerJson($file->getPathname());
+        } catch (\Exception $exception) {
+            $this->io->write('Failed loading package '.$file->getPathname().': '.$exception->getMessage(), false, IOInterface::VERBOSE);
+        }
 
         if (null === $json) {
             return false;
diff --git a/src/Composer/Util/Zip.php b/src/Composer/Util/Zip.php
index 3ebdcdd85..ad6617edf 100644
--- a/src/Composer/Util/Zip.php
+++ b/src/Composer/Util/Zip.php
@@ -66,8 +66,9 @@ class Zip
      *
      * @param \ZipArchive $zip
      * @param string      $filename
+     * @throws \RuntimeException
      *
-     * @return bool|int
+     * @return int
      */
     private static function locateFile(\ZipArchive $zip, $filename)
     {
@@ -85,8 +86,7 @@ class Zip
             if ($dirname === '.') {
                 $topLevelPaths[$name] = true;
                 if (\count($topLevelPaths) > 1) {
-                    // archive can only contain one top level directory
-                    return false;
+                    throw new \RuntimeException('Archive has more than one top level directories, and no composer.json was found on the top level, so it\'s an invalid archive. Top level paths found were: '.implode(',', array_keys($topLevelPaths)));
                 }
                 continue;
             }
@@ -95,8 +95,7 @@ class Zip
             if (false === strpos('\\', $dirname) && false === strpos('/', $dirname)) {
                 $topLevelPaths[$dirname.'/'] = true;
                 if (\count($topLevelPaths) > 1) {
-                    // archive can only contain one top level directory
-                    return false;
+                    throw new \RuntimeException('Archive has more than one top level directories, and no composer.json was found on the top level, so it\'s an invalid archive. Top level paths found were: '.implode(',', array_keys($topLevelPaths)));
                 }
             }
         }
@@ -105,7 +104,6 @@ class Zip
             return $index;
         }
 
-        // no composer.json found either at the top level or within the topmost directory
-        return false;
+        throw new \RuntimeException('No composer.json found either at the top level or within the topmost directory');
     }
 }
diff --git a/tests/Composer/Test/Util/Fixtures/Zip/multiple_subfolders.zip b/tests/Composer/Test/Util/Fixtures/Zip/multiple_subfolders.zip
new file mode 100644
index 000000000..5c5bc5adf
Binary files /dev/null and b/tests/Composer/Test/Util/Fixtures/Zip/multiple_subfolders.zip differ
diff --git a/tests/Composer/Test/Util/ZipTest.php b/tests/Composer/Test/Util/ZipTest.php
index 78c7e9657..ba61e8bf6 100644
--- a/tests/Composer/Test/Util/ZipTest.php
+++ b/tests/Composer/Test/Util/ZipTest.php
@@ -55,28 +55,30 @@ class ZipTest extends TestCase
         $this->assertNull($result);
     }
 
-    public function testReturnsNullIfTheZipHasNoComposerJson()
+    /**
+     * @expectedException \RuntimeException
+     */
+    public function testThrowsExceptionIfTheZipHasNoComposerJson()
     {
         if (!extension_loaded('zip')) {
             $this->markTestSkipped('The PHP zip extension is not loaded.');
             return;
         }
 
-        $result = Zip::getComposerJson(__DIR__.'/Fixtures/Zip/nojson.zip');
-
-        $this->assertNull($result);
+        Zip::getComposerJson(__DIR__.'/Fixtures/Zip/nojson.zip');
     }
 
-    public function testReturnsNullIfTheComposerJsonIsInASubSubfolder()
+    /**
+     * @expectedException \RuntimeException
+     */
+    public function testThrowsExceptionIfTheComposerJsonIsInASubSubfolder()
     {
         if (!extension_loaded('zip')) {
             $this->markTestSkipped('The PHP zip extension is not loaded.');
             return;
         }
 
-        $result = Zip::getComposerJson(__DIR__.'/Fixtures/Zip/subfolders.zip');
-
-        $this->assertNull($result);
+        Zip::getComposerJson(__DIR__.'/Fixtures/Zip/subfolders.zip');
     }
 
     public function testReturnsComposerJsonInZipRoot()
@@ -99,10 +101,12 @@ class ZipTest extends TestCase
         }
 
         $result = Zip::getComposerJson(__DIR__.'/Fixtures/Zip/folder.zip');
-
         $this->assertEquals("{\n    \"name\": \"foo/bar\"\n}\n", $result);
     }
 
+    /**
+     * @expectedException \RuntimeException
+     */
     public function testMultipleTopLevelDirsIsInvalid()
     {
         if (!extension_loaded('zip')) {
@@ -110,9 +114,7 @@ class ZipTest extends TestCase
             return;
         }
 
-        $result = Zip::getComposerJson(__DIR__.'/Fixtures/Zip/multiple.zip');
-
-        $this->assertNull($result);
+        Zip::getComposerJson(__DIR__.'/Fixtures/Zip/multiple.zip');
     }
 
     public function testReturnsComposerJsonFromFirstSubfolder()
@@ -126,4 +128,17 @@ class ZipTest extends TestCase
 
         $this->assertEquals("{\n    \"name\": \"foo/bar\"\n}\n", $result);
     }
+
+    /**
+     * @expectedException \RuntimeException
+     */
+    public function testThrowsExceptionIfMultipleComposerInSubFoldersWereFound()
+    {
+        if (!extension_loaded('zip')) {
+            $this->markTestSkipped('The PHP zip extension is not loaded.');
+            return;
+        }
+
+        Zip::getComposerJson(__DIR__.'/Fixtures/Zip/multiple_subfolders.zip');
+    }
 }