diff --git a/src/RTEX/Abstracts/VariableType.php b/src/RTEX/Abstracts/VariableType.php
index 2d84802..4f3c563 100644
--- a/src/RTEX/Abstracts/VariableType.php
+++ b/src/RTEX/Abstracts/VariableType.php
@@ -20,6 +20,8 @@
 
         const Instruction = 'instruction';
 
+        const Unknown = 'unknown';
+
         const All = [
             self::String,
             self::Integer,