diff --git a/src/Composer/Autoload/ClassMapGenerator.php b/src/Composer/Autoload/ClassMapGenerator.php
index f8f18fc28..862e44ba2 100644
--- a/src/Composer/Autoload/ClassMapGenerator.php
+++ b/src/Composer/Autoload/ClassMapGenerator.php
@@ -112,7 +112,10 @@ class ClassMapGenerator
      */
     private static function findClasses($path)
     {
-        $traits = version_compare(PHP_VERSION, '5.4', '<') ? '' : '|trait';
+        $extraTypes = version_compare(PHP_VERSION, '5.4', '<') ? '' : '|trait';
+        if (defined('HHVM_VERSION') && version_compare(HHVM_VERSION, '3.3', '>=')) {
+            $extraTypes .= '|enum';
+        }
 
         try {
             $contents = @php_strip_whitespace($path);
@@ -129,7 +132,7 @@ class ClassMapGenerator
         }
 
         // return early if there is no chance of matching anything in this file
-        if (!preg_match('{\b(?:class|interface'.$traits.')\s}i', $contents)) {
+        if (!preg_match('{\b(?:class|interface'.$extraTypes.')\s}i', $contents)) {
             return array();
         }
 
@@ -154,7 +157,7 @@ class ClassMapGenerator
 
         preg_match_all('{
             (?:
-                 \b(?<![\$:>])(?P<type>class|interface'.$traits.') \s+ (?P<name>[a-zA-Z_\x7f-\xff:][a-zA-Z0-9_\x7f-\xff:\-]*)
+                 \b(?<![\$:>])(?P<type>class|interface'.$extraTypes.') \s+ (?P<name>[a-zA-Z_\x7f-\xff:][a-zA-Z0-9_\x7f-\xff:\-]*)
                | \b(?<![\$:>])(?P<ns>namespace) (?P<nsname>\s+[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*(?:\s*\\\\\s*[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)*)? \s*[\{;]
             )
         }ix', $contents, $matches);
@@ -170,6 +173,12 @@ class ClassMapGenerator
                 if ($name[0] === ':') {
                     // This is an XHP class, https://github.com/facebook/xhp
                     $name = 'xhp'.substr(str_replace(array('-', ':'), array('_', '__'), $name), 1);
+                } else if ($matches['type'][$i] === 'enum') {
+                    // In Hack, something like:
+                    //   enum Foo: int { HERP = '123'; }
+                    // The regex above captures the colon, which isn't part of
+                    // the class name.
+                    $name = rtrim($name, ':');
                 }
                 $classes[] = ltrim($namespace . $name, '\\');
             }
diff --git a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
index 81f99e57b..b8efc0c80 100644
--- a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
+++ b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
@@ -74,6 +74,13 @@ class ClassMapGeneratorTest extends \PHPUnit_Framework_TestCase
                 'Foo\\CBar' => __DIR__.'/Fixtures/php5.4/traits.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',
+                'Foo\BarEnum' => __DIR__.'/Fixtures/hhvm3.3/NamespacedHackEnum.php',
+                'GenericsClass' => __DIR__.'/Fixtures/hhvm3.3/Generics.php',
+            ));
+        }
 
         return $data;
     }
diff --git a/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/Generics.php b/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/Generics.php
new file mode 100644
index 000000000..e5d1aa12a
--- /dev/null
+++ b/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/Generics.php
@@ -0,0 +1,4 @@
+<?hh
+
+class GenericsClass<Tk, Tv> {
+}
diff --git a/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/HackEnum.php b/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/HackEnum.php
new file mode 100644
index 000000000..4b8dbfd40
--- /dev/null
+++ b/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/HackEnum.php
@@ -0,0 +1,6 @@
+<?hh
+
+enum FooEnum: int {
+  HERP = 1;
+  DERP = 2;
+}
diff --git a/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/NamespacedHackEnum.php b/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/NamespacedHackEnum.php
new file mode 100644
index 000000000..9e0f9d14e
--- /dev/null
+++ b/tests/Composer/Test/Autoload/Fixtures/hhvm3.3/NamespacedHackEnum.php
@@ -0,0 +1,7 @@
+<?hh
+
+namespace Foo;
+
+enum BarEnum: string {
+  HERP = 'DERP';
+}