diff --git a/src/Graph/Calc.php b/src/Graph/Calc.php
index 276c90a..bf9cb16 100644
--- a/src/Graph/Calc.php
+++ b/src/Graph/Calc.php
@@ -30,7 +30,7 @@ class Calc
             eval($this->params);
             eval($this->formulas);
             if ($y->getParsed() != '') {
-                eval('$result = ' . $y->getParsed() . ';');
+                eval('@$result = ' . $y->getParsed() . ';');
                 $y->setResult($result);
             }
         }