diff --git a/src/Valitron/Validator.php b/src/Valitron/Validator.php
index 6952586..74e41c6 100644
--- a/src/Valitron/Validator.php
+++ b/src/Valitron/Validator.php
@@ -1021,7 +1021,8 @@ class Validator
      * Should the validation stop a rule is failed
      * @param bool $stop
      */
-    public function stopOnFirstFail(bool $stop) {
+    public function stopOnFirstFail($stop) {
+    	if(!is_bool($stop)) throw new \InvalidArgumentException('Parameter of type boolean expected');
     	$this->stop_on_first_fail = $stop;
     }