diff --git a/htdocs/core/class/evalmath.class.php b/htdocs/core/class/evalmath.class.php
index ccd495bb623..78221de5c98 100644
--- a/htdocs/core/class/evalmath.class.php
+++ b/htdocs/core/class/evalmath.class.php
@@ -374,7 +374,7 @@ class EvalMath
 	 */
 	private function pfx($tokens, $vars = array())
 	{
-		if ($tokens == false) {
+		if (empty($tokens)) {
 			return false;
 		}