diff --git a/src/Compiler.php b/src/Compiler.php
index c7f504c..afdeb5c 100644
--- a/src/Compiler.php
+++ b/src/Compiler.php
@@ -1638,7 +1638,7 @@ final public function expression(array $expr, bool $doubleQuotes = false): strin
 
             switch ($type) {
                 case static::PHVOLT_T_NOT:
-                    $exprCode = '|' . $rightCode;
+                    $exprCode = '!' . $rightCode;
                     break;
 
                 case static::PHVOLT_T_MUL: