diff --git a/composer.json b/composer.json
index 8e9ba218a..6251e3f19 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
     },
     "require": {
         "php": "^5.3.2 || ^7.0",
-        "justinrainbow/json-schema": "^1.6 || ^2.0 || ^3.0 || ^4.0",
+        "justinrainbow/json-schema": "^3.0 || ^4.0",
         "composer/ca-bundle": "^1.0",
         "composer/semver": "^1.0",
         "composer/spdx-licenses": "^1.0",
diff --git a/composer.lock b/composer.lock
index 331413f0c..9925bc490 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"
     ],
-    "content-hash": "deb4df08cdd39eac7d11880586076ba1",
+    "content-hash": "e18501d127e13e3619f80abbcf372c81",
     "packages": [
         {
             "name": "composer/ca-bundle",
diff --git a/src/Composer/Json/JsonFile.php b/src/Composer/Json/JsonFile.php
index 32e6d129e..1a33992f3 100644
--- a/src/Composer/Json/JsonFile.php
+++ b/src/Composer/Json/JsonFile.php
@@ -157,7 +157,13 @@ class JsonFile
         }
 
         $schemaFile = __DIR__ . '/../../../res/composer-schema.json';
-        $schemaData = json_decode(file_get_contents($schemaFile));
+
+        // Prepend with file:// only when not using a special schema already (e.g. in the phar)
+        if (false === strpos($schemaFile, '://')) {
+            $schemaFile = 'file://' . $schemaFile;
+        }
+
+        $schemaData = (object) array('$ref' => $schemaFile);
 
         if ($schema === self::LAX_SCHEMA) {
             $schemaData->additionalProperties = true;