diff --git a/composer.json b/composer.json
index c7274646f5..d28912cdef 100644
--- a/composer.json
+++ b/composer.json
@@ -26,13 +26,7 @@
   "autoload": {
     "psr-4": {
       "Roots\\Sage\\": "src/lib/Sage/"
-    },
-    "files": [
-      "src/helpers.php",
-      "src/setup.php",
-      "src/filters.php",
-      "src/admin.php"
-    ]
+    }
   },
   "require": {
     "php": ">=5.5.0",
diff --git a/composer.lock b/composer.lock
index 3bb9cda00f..6f8b895c9a 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "hash": "bae0265fe64b728b3ad0fd3ab2ca2df0",
+    "hash": "7382dc6bb77190896306e1eb58b6589c",
     "content-hash": "75ad99c892e1d82404c58fe3bd989585",
     "packages": [
         {
diff --git a/functions.php b/functions.php
index f8eecbb53d..6d43a4c068 100644
--- a/functions.php
+++ b/functions.php
@@ -23,6 +23,31 @@
     basename($stylesheet) == 'templates' || update_option('stylesheet', $stylesheet . '/templates');
 });
 
+/**
+ * Sage includes
+ *
+ * The $sage_includes array determines the code library included in your theme.
+ * Add or remove files to the array as needed. Supports child theme overrides.
+ *
+ * Please note that missing files will produce a fatal error.
+ *
+ * @link https://github.com/roots/sage/pull/1042
+ */
+$sage_includes = [
+    'src/helpers.php',    // Helper functions
+    'src/setup.php',      // Theme setup
+    'src/filters.php',    // Filters
+    'src/admin.php'       // Admin
+];
+
+foreach ($sage_includes as $file) {
+    if (!$filepath = locate_template($file)) {
+        trigger_error(sprintf(__('Error locating %s for inclusion', 'sage'), $file), E_USER_ERROR);
+    }
+    require_once $filepath;
+}
+unset($file, $filepath);
+
 /**
  * Require composer autoloader
  */