diff --git a/src/IDF/Project.php b/src/IDF/Project.php
index 0a63504..641ad79 100644
--- a/src/IDF/Project.php
+++ b/src/IDF/Project.php
@@ -319,4 +319,20 @@ class IDF_Project extends Pluf_Model
         // containing a series of git repositories
         return $gitrep.'/'.$this->shortname.'.git';
     }
+
+    /**
+     * Check that the object belongs to the project or rise a 404
+     * error.
+     *
+     * By convention, all the objects belonging to a project have the
+     * 'project' property set, so this is easy to check.
+     *
+     * @param Pluf_Model 
+     */
+    public function inOr404($obj)
+    {
+        if ($obj->project != $this->id) {
+            throw new Pluf_HTTP_Error404();
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/IDF/Views/Download.php b/src/IDF/Views/Download.php
index b973b85..683afb2 100644
--- a/src/IDF/Views/Download.php
+++ b/src/IDF/Views/Download.php
@@ -77,9 +77,7 @@ class IDF_Views_Download
     {
         $prj = $request->project;
         $upload = Pluf_Shortcuts_GetObjectOr404('IDF_Upload', $match[2]);
-        if ($upload->project != $prj->id) {
-            throw new Pluf_HTTP_Error404();
-        }
+        $prj->inOr404($upload);
         $title = sprintf(__('Download %s'), $upload->summary);
         $form = false;
         if ($request->method == 'POST' and
@@ -121,9 +119,7 @@ class IDF_Views_Download
     {
         $prj = $request->project;
         $upload = Pluf_Shortcuts_GetObjectOr404('IDF_Upload', $match[2]);
-        if ($upload->project != $prj->id) {
-            throw new Pluf_HTTP_Error404();
-        }
+        $prj->inOr404($upload);
         $upload->downloads += 1;
         $upload->update();
         return new Pluf_HTTP_Response_Redirect($upload->getAbsoluteUrl($prj));
@@ -199,8 +195,6 @@ class IDF_Views_Download
  */
 function IDF_Views_Download_SummaryAndLabels($field, $down, $extra='')
 {
-    //$edit = Pluf_HTTP_URL_urlForView('IDF_Views_Download::view', 
-    //                                     array($down->shortname, $down->id));
     $tags = array();
     foreach ($down->get_tags_list() as $tag) {
         $tags[] = sprintf('<span class="label">%s</span>', Pluf_esc((string) $tag));
diff --git a/src/IDF/Views/Issue.php b/src/IDF/Views/Issue.php
index 9892f42..9b4153a 100644
--- a/src/IDF/Views/Issue.php
+++ b/src/IDF/Views/Issue.php
@@ -161,9 +161,7 @@ class IDF_Views_Issue
     {
         $prj = $request->project;
         $issue = Pluf_Shortcuts_GetObjectOr404('IDF_Issue', $match[2]);
-        if ($issue->project != $prj->id) {
-            throw new Pluf_HTTP_Error404();
-        }
+        $prj->inOr404($issue);
         $comments = $issue->get_comments_list(array('order' => 'id ASC'));
         $url = Pluf_HTTP_URL_urlForView('IDF_Views_Issue::view',
                                         array($prj->shortname, $issue->id));