diff --git a/src/Composer/Autoload/ClassMapGenerator.php b/src/Composer/Autoload/ClassMapGenerator.php
index 704d6b39f..5eed9523c 100644
--- a/src/Composer/Autoload/ClassMapGenerator.php
+++ b/src/Composer/Autoload/ClassMapGenerator.php
@@ -188,6 +188,10 @@ class ClassMapGenerator
                 $namespace = str_replace(array(' ', "\t", "\r", "\n"), '', $matches['nsname'][$i]) . '\\';
             } else {
                 $name = $matches['name'][$i];
+                // skip anon classes extending/implementing
+                if ($name === 'extends' || $name === 'implements') {
+                    continue;
+                }
                 if ($name[0] === ':') {
                     // This is an XHP class, https://github.com/facebook/xhp
                     $name = 'xhp'.substr(str_replace(array('-', ':'), array('_', '__'), $name), 1);
diff --git a/src/Composer/Plugin/PluginManager.php b/src/Composer/Plugin/PluginManager.php
index d77337809..6f6d946b4 100644
--- a/src/Composer/Plugin/PluginManager.php
+++ b/src/Composer/Plugin/PluginManager.php
@@ -179,9 +179,14 @@ class PluginManager
 
         foreach ($classes as $class) {
             if (class_exists($class, false)) {
+                $class = trim($class, '\\');
                 $path = $classLoader->findFile($class);
                 $code = file_get_contents($path);
-                $code = preg_replace('{^((?:final\s+)?(?:\s*))class\s+(\S+)}mi', '$1class $2_composer_tmp'.self::$classCounter, $code);
+                $separatorPos = strrpos($class, '\\');
+                if ($separatorPos) {
+                    $className = substr($class, $separatorPos + 1);
+                }
+                $code = preg_replace('{^((?:final\s+)?(?:\s*))class\s+(\S+)}mi', '$1class $2_composer_tmp'.self::$classCounter, $code, 1);
                 $code = str_replace('__FILE__', var_export($path, true), $code);
                 $code = str_replace('__DIR__', var_export(dirname($path), true), $code);
                 $code = str_replace('__CLASS__', var_export($class, true), $code);
diff --git a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
index 13cf7cd83..4af707160 100644
--- a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
+++ b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
@@ -87,6 +87,11 @@ class ClassMapGeneratorTest extends TestCase
                 'Foo\\CBar' => __DIR__.'/Fixtures/php5.4/traits.php',
             ));
         }
+        if (PHP_VERSION_ID >= 70000) {
+            $data[] = array(__DIR__.'/Fixtures/php7.0', array(
+                'Dummy\Test\AnonClassHolder' => __DIR__.'/Fixtures/php7.0/anonclass.php',
+            ));
+        }
         if (defined('HHVM_VERSION') && version_compare(HHVM_VERSION, '3.3', '>=')) {
             $data[] = array(__DIR__.'/Fixtures/hhvm3.3', array(
                 'FooEnum' => __DIR__.'/Fixtures/hhvm3.3/HackEnum.php',
diff --git a/tests/Composer/Test/Autoload/Fixtures/php7.0/anonclass.php b/tests/Composer/Test/Autoload/Fixtures/php7.0/anonclass.php
new file mode 100644
index 000000000..44176abe1
--- /dev/null
+++ b/tests/Composer/Test/Autoload/Fixtures/php7.0/anonclass.php
@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Dummy\Test;
+
+use Dummy\Common\TestCase;
+
+class AnonClassHolder extends TestCase
+{
+    protected function getTest(): ClassAvailability
+    {
+        return new class extends ClassAvailability
+        {
+        };
+    }
+
+    protected function getTest2(): ClassAvailability
+    {
+        return new class(2) extends ClassAvailability
+        {
+        };
+    }
+
+    protected function getTest3(): ClassAvailability
+    {
+        return new class(2, 3) extends ClassAvailability
+        {
+        };
+    }
+
+    protected function getTest4(): ClassAvailability
+    {
+        return new class(2, 3) {
+        };
+    }
+
+    protected function getTest5(): ClassAvailability
+    {
+        return new class implements FooInterface {
+        };
+    }
+}