diff --git a/src/Illuminate/Database/Query/Builder.php b/src/Illuminate/Database/Query/Builder.php
index 4841827259c9..018f04ab902b 100755
--- a/src/Illuminate/Database/Query/Builder.php
+++ b/src/Illuminate/Database/Query/Builder.php
@@ -837,8 +837,8 @@ protected function invalidOperatorAndValue($operator, $value)
      */
     protected function invalidOperator($operator)
     {
-        return ! in_array(strtolower($operator), $this->operators, true) &&
-               ! in_array(strtolower($operator), $this->grammar->getOperators(), true);
+        return ! is_string($operator) || (! in_array(strtolower($operator), $this->operators, true) &&
+               ! in_array(strtolower($operator), $this->grammar->getOperators(), true));
     }
 
     /**