diff --git a/doc/04-schema.md b/doc/04-schema.md
index b777416ed..f5440fba7 100644
--- a/doc/04-schema.md
+++ b/doc/04-schema.md
@@ -416,7 +416,8 @@ use an empty prefix like:
 
 The `classmap` references are all combined, during install/update, into a single
 key => value array which may be found in the generated file
-`vendor/composer/autoload_classmap.php`.
+`vendor/composer/autoload_classmap.php`. This map is built by scanning for
+classes in all `.php` and `.inc` files in the given directories/files.
 
 You can use the classmap generation support to define autoloading for all libraries
 that do not follow PSR-0. To configure this you specify all directories or files
diff --git a/src/Composer/Autoload/ClassMapGenerator.php b/src/Composer/Autoload/ClassMapGenerator.php
index 26f3cf28e..5a74728f2 100644
--- a/src/Composer/Autoload/ClassMapGenerator.php
+++ b/src/Composer/Autoload/ClassMapGenerator.php
@@ -71,7 +71,7 @@ class ClassMapGenerator
 
             $filePath = $file->getRealPath();
 
-            if (pathinfo($filePath, PATHINFO_EXTENSION) !== 'php') {
+            if (!in_array(pathinfo($filePath, PATHINFO_EXTENSION), array('php', 'inc'))) {
                 continue;
             }
 
diff --git a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
index 9f5606e0c..40d79849c 100644
--- a/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
+++ b/tests/Composer/Test/Autoload/ClassMapGeneratorTest.php
@@ -27,7 +27,7 @@ class ClassMapGeneratorTest extends \PHPUnit_Framework_TestCase
     {
         $data = array(
             array(__DIR__.'/Fixtures/Namespaced', array(
-                'Namespaced\\Bar' => realpath(__DIR__).'/Fixtures/Namespaced/Bar.php',
+                'Namespaced\\Bar' => realpath(__DIR__).'/Fixtures/Namespaced/Bar.inc',
                 'Namespaced\\Foo' => realpath(__DIR__).'/Fixtures/Namespaced/Foo.php',
                 'Namespaced\\Baz' => realpath(__DIR__).'/Fixtures/Namespaced/Baz.php',
             )),
diff --git a/tests/Composer/Test/Autoload/Fixtures/Namespaced/Bar.php b/tests/Composer/Test/Autoload/Fixtures/Namespaced/Bar.inc
similarity index 100%
rename from tests/Composer/Test/Autoload/Fixtures/Namespaced/Bar.php
rename to tests/Composer/Test/Autoload/Fixtures/Namespaced/Bar.inc