diff --git a/src/Composer/Autoload/AutoloadGenerator.php b/src/Composer/Autoload/AutoloadGenerator.php
index 0de53a3bf..20f8c7570 100644
--- a/src/Composer/Autoload/AutoloadGenerator.php
+++ b/src/Composer/Autoload/AutoloadGenerator.php
@@ -40,7 +40,7 @@ class AutoloadGenerator
 
     private $devMode = false;
 
-    public function __construct(EventDispatcher $eventDispatcher, IOInterface $io=null)
+    public function __construct(EventDispatcher $eventDispatcher, IOInterface $io = null)
     {
         $this->eventDispatcher = $eventDispatcher;
         $this->io = $io;
@@ -184,7 +184,7 @@ EOF;
                             preg_quote($dir),
                             ($psrType === 'psr-0' && strpos($namespace, '_') === false) ? preg_quote(strtr($namespace, '\\', '/')) : ''
                         );
-                        foreach (ClassMapGenerator::createMap($dir, $whitelist) as $class => $path) {
+                        foreach (ClassMapGenerator::createMap($dir, $whitelist, $this->io) as $class => $path) {
                             if ('' === $namespace || 0 === strpos($class, $namespace)) {
                                 if (!isset($classMap[$class])) {
                                     $path = $this->getPathCode($filesystem, $basePath, $vendorPath, $path);
@@ -198,18 +198,12 @@ EOF;
         }
 
         foreach ($autoloads['classmap'] as $dir) {
-            foreach (ClassMapGenerator::createMap($dir) as $class => $path) {
+            foreach (ClassMapGenerator::createMap($dir, null, $this->io) as $class => $path) {
                 $path = $this->getPathCode($filesystem, $basePath, $vendorPath, $path);
                 $classMap[$class] = $path.",\n";
             }
         }
 
-        if ($this->io && count(ClassMapGenerator::$ambiguousReferences) > 0) {
-            foreach (ClassMapGenerator::$ambiguousReferences as $ambiguousReference) {
-                $this->io->write('<info>Warning: Ambiguous class "'.$ambiguousReference['class'].'" resolution; defined in "'.$ambiguousReference[0].'" and in "'.$ambiguousReference[1].'" files.</info>');
-            }
-        }
-
         ksort($classMap);
         foreach ($classMap as $class => $code) {
             $classmapFile .= '    '.var_export($class, true).' => '.$code;
diff --git a/src/Composer/Autoload/ClassMapGenerator.php b/src/Composer/Autoload/ClassMapGenerator.php
index 4805e7308..719a16102 100644
--- a/src/Composer/Autoload/ClassMapGenerator.php
+++ b/src/Composer/Autoload/ClassMapGenerator.php
@@ -12,21 +12,18 @@
  */
 
 namespace Composer\Autoload;
+
 use Symfony\Component\Finder\Finder;
+use Composer\IO\IOInterface;
 
 /**
  * ClassMapGenerator
  *
  * @author Gyula Sallai <salla016@gmail.com>
+ * @author Jordi Boggiano <j.boggiano@seld.be>
  */
 class ClassMapGenerator
 {
-
-    /**
-     * @var array
-     */
-    public static $ambiguousReferences = array();
-
     /**
      * Generate a class map file
      *
@@ -54,7 +51,7 @@ class ClassMapGenerator
      *
      * @throws \RuntimeException When the path is neither an existing file nor directory
      */
-    public static function createMap($path, $whitelist = null)
+    public static function createMap($path, $whitelist = null, IOInterface $io = null)
     {
         if (is_string($path)) {
             if (is_file($path)) {
@@ -85,15 +82,14 @@ class ClassMapGenerator
             $classes = self::findClasses($filePath);
 
             foreach ($classes as $class) {
-                if (array_key_exists($class, $map)) {
-                    self::$ambiguousReferences[] = array(
-                        'class' => $class,
-                        '0' => $map[$class],
-                        '1' => $filePath
+                if (!isset($map[$class])) {
+                    $map[$class] = $filePath;
+                } elseif ($io) {
+                    $io->write(
+                        '<warning>Warning: Ambiguous class resolution, "'.$class.'"'.
+                        ' was found in both "'.$map[$class].'" and "'.$filePath.'", the first will be used.</warning>'
                     );
                 }
-
-                $map[$class] = $filePath;
             }
         }
 
diff --git a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
index 6b5049830..1a855558f 100644
--- a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
+++ b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
@@ -109,10 +109,18 @@ class ClassMapGeneratorTest extends \PHPUnit_Framework_TestCase
         $finder = new Finder();
         $finder->files()->in(__DIR__ . '/Fixtures/Ambiguous');
 
-        ClassMapGenerator::createMap($finder);
+        $io = $this->getMockBuilder('Composer\IO\ConsoleIO')
+            ->disableOriginalConstructor()
+            ->getMock();
 
-        $this->assertEquals(1, count(ClassMapGenerator::$ambiguousReferences));
-        $this->assertEquals('A', ClassMapGenerator::$ambiguousReferences[0]['class']);
+        $a = realpath(__DIR__.'/Fixtures/Ambiguous/A.php');
+        $b = realpath(__DIR__.'/Fixtures/Ambiguous/other/A.php');
+
+        $io->expects($this->once())
+            ->method('write')
+            ->with('<warning>Warning: Ambiguous class resolution, "A" was found in both "'.$a.'" and "'.$b.'", the first will be used.</warning>');
+
+        ClassMapGenerator::createMap($finder, null, $io);
     }
 
     /**