diff --git a/src/Spout/Writer/Common/Helper/CellHelper.php b/src/Spout/Writer/Common/Helper/CellHelper.php
index 50ead93..1caf811 100644
--- a/src/Spout/Writer/Common/Helper/CellHelper.php
+++ b/src/Spout/Writer/Common/Helper/CellHelper.php
@@ -61,6 +61,9 @@ class CellHelper
      */
     public static function isNonEmptyString($value)
     {
+        if (is_object($value) && method_exists($value, '__toString')) {
+            $value = $value->__toString();
+        }
         return (gettype($value) === 'string' && $value !== '');
     }