diff --git a/index.php b/index.php
index 0e30d16bdfa..c07e20fbfed 100644
--- a/index.php
+++ b/index.php
@@ -1247,7 +1247,7 @@ function checkUploadedFileValidity($move, $backok=null)
                     else
                         $filecount = 0;
 
-                    if ($filecount < $validation['min_num_of_files'] && LimeExpressionManager::QuestionIsRelevant($fieldmap[$field]['qid']))
+                    if (isset($validation['min_num_of_files']) && $filecount < $validation['min_num_of_files'] && LimeExpressionManager::QuestionIsRelevant($fieldmap[$field]['qid']))
                     {
                         $filenotvalidated = array();
                         $filenotvalidated[$field] = $clang->gT("The minimum number of files has not been uploaded.");