diff --git a/bin/composer-require-checker-config.json b/bin/composer-require-checker-config.json
index ec59c89fd..34acbc19e 100644
--- a/bin/composer-require-checker-config.json
+++ b/bin/composer-require-checker-config.json
@@ -2,7 +2,9 @@
   "symbol-whitelist" : [
     "null", "true", "false",
     "static", "self", "parent",
-    "array", "string", "int", "float", "bool", "iterable", "callable", "void", "object"
+    "array", "string", "int", "float", "bool", "iterable", "callable", "void", "object",
+    "igbinary_serialize", "igbinary_unserialize", "PHP_PARSER_VERSION", "PSALM_VERSION", "runkit_object_id",
+    "sapi_windows_cp_is_utf8"
   ],
   "php-core-extensions" : [
     "Core",
diff --git a/src/Psalm/Internal/PluginManager/ConfigFile.php b/src/Psalm/Internal/PluginManager/ConfigFile.php
index d9049a82d..fb18bad6f 100644
--- a/src/Psalm/Internal/PluginManager/ConfigFile.php
+++ b/src/Psalm/Internal/PluginManager/ConfigFile.php
@@ -1,7 +1,7 @@
 <?php
 namespace Psalm\Internal\PluginManager;
 
-use DomDocument;
+use DOMDocument;
 use function file_get_contents;
 use function file_put_contents;
 use Psalm\Config;
@@ -106,9 +106,9 @@ class ConfigFile
         $this->saveXml($config_xml);
     }
 
-    private function readXml(): DomDocument
+    private function readXml(): DOMDocument
     {
-        $doc = new DomDocument();
+        $doc = new DOMDocument();
 
         $file_contents = file_get_contents($this->path);
 
@@ -127,7 +127,7 @@ class ConfigFile
     }
 
     /** @return void */
-    private function saveXml(DomDocument $config_xml)
+    private function saveXml(DOMDocument $config_xml)
     {
         $new_file_contents = $config_xml->saveXML($config_xml);