diff --git a/QueryProcessor.php b/QueryProcessor.php
index deacb50..88a8b30 100644
--- a/QueryProcessor.php
+++ b/QueryProcessor.php
@@ -332,7 +332,7 @@ protected function filterInCondition(array $data, $operator, $operands)
 
         $values = (array) $values;
 
-        if (count($column) > 1) {
+        if (count((array) $column) > 1) {
             throw new InvalidParamException("Operator '$operator' allows only a single column.");
         }