diff --git a/src/permission/PermissionParser.php b/src/permission/PermissionParser.php
index d498b9315..cc54f270e 100644
--- a/src/permission/PermissionParser.php
+++ b/src/permission/PermissionParser.php
@@ -53,6 +53,10 @@ class PermissionParser{
 		"false" => self::DEFAULT_FALSE,
 	];
 
+	private const KEY_DEFAULT = "default";
+	private const KEY_CHILDREN = "children";
+	private const KEY_DESCRIPTION = "description";
+
 	/**
 	 * @param bool|string $value
 	 *
@@ -86,16 +90,16 @@ class PermissionParser{
 		$result = [];
 		foreach(Utils::stringifyKeys($data) as $name => $entry){
 			$desc = null;
-			if(isset($entry["default"])){
-				$default = PermissionParser::defaultFromString($entry["default"]);
+			if(isset($entry[self::KEY_DEFAULT])){
+				$default = PermissionParser::defaultFromString($entry[self::KEY_DEFAULT]);
 			}
 
-			if(isset($entry["children"])){
+			if(isset($entry[self::KEY_CHILDREN])){
 				throw new PermissionParserException("Nested permission declarations are no longer supported. Declare each permission separately.");
 			}
 
-			if(isset($entry["description"])){
-				$desc = $entry["description"];
+			if(isset($entry[self::KEY_DESCRIPTION])){
+				$desc = $entry[self::KEY_DESCRIPTION];
 			}
 
 			$result[$default][] = new Permission($name, $desc);