diff --git a/ktapi/KTAPIDocument.inc.php b/ktapi/KTAPIDocument.inc.php
index 56e26a7..d3d17ae 100644
--- a/ktapi/KTAPIDocument.inc.php
+++ b/ktapi/KTAPIDocument.inc.php
@@ -1159,10 +1159,10 @@ class KTAPI_Document extends KTAPI_FolderItem
 					$indexContent = $value;
 					break;
 				case 'created_date':
-					$documents['created'] = $value;
+					if (!empty($value)) $documents['created'] = $value;
 					break;
 				case 'modified_date':
-					$documents['modified'] = $value;
+					if (!empty($value)) $documents['modified'] = $value;
 					break;
 				case 'is_immutable':
 					$documents['immutable'] = in_array(strtolower($value), array('1','true','on','yes'))?'1':'0';