diff --git a/src/IDF/Form/Upload.php b/src/IDF/Form/Upload.php
index e13e468..a88c2c3 100644
--- a/src/IDF/Form/Upload.php
+++ b/src/IDF/Form/Upload.php
@@ -70,6 +70,9 @@ class IDF_Form_Upload extends Pluf_Form
         if (!preg_match('/\.(png|jpg|jpeg|gif|bmp|psd|tif|aiff|asf|avi|bz2|css|doc|eps|gz|mdtext|mid|mov|mp3|mpg|ogg|pdf|ppt|ps|qt|ra|ram|rm|rtf|sdd|sdw|sit|sxi|sxw|swf|tgz|txt|wav|xls|xml|wmv|zip)$/i', $this->cleaned_data['file'])) {
             throw new Pluf_Form_Invalid(__('For security reason, you cannot upload a file with this extension.'));
         }
+        if (file_exists(Pluf::f('upload_path').'/'.$this->project->shortname.'/files/'.$this->cleaned_data['file'])) {
+            throw new Pluf_Form_Invalid(sprintf(__('A file with the name "%s" is already available for download.'), $this->cleaned_data['file']));
+        }
         return $this->cleaned_data['file'];
     }