diff --git a/main/inc/lib/fileDisplay.lib.php b/main/inc/lib/fileDisplay.lib.php
index 469a9ef569..694e5350e9 100644
--- a/main/inc/lib/fileDisplay.lib.php
+++ b/main/inc/lib/fileDisplay.lib.php
@@ -237,21 +237,21 @@ function get_total_folder_size($path, $can_see_invisible = false) {
     
     $course_id 			= api_get_course_int_id();
     $session_id         = api_get_session_id();
-    $session_condition  = api_get_session_condition($session_id, true, true, 'id_session');
+    $session_condition  = api_get_session_condition($session_id, true, true, 'props.id_session');
 
-    $visibility_rule = 'props.visibility ' . ($can_see_invisible ? '<> 2' : '= 1');
+    $visibility_rule = ' props.visibility ' . ($can_see_invisible ? '<> 2' : '= 1');
     
     $sql = "SELECT SUM(table1.size) FROM (
                 SELECT size FROM $table_itemproperty AS props, $table_document AS docs
-                WHERE 	docs.c_id 	= $course_id AND
-                        props.c_id 	= $course_id AND    		
+                WHERE 	docs.c_id 	= $course_id AND                        
                         docs.id 	= props.ref AND 
-                        props.tool 	= '$tool_document' AND 
-                        path LIKE '$path/%' AND                     
-                        $visibility_rule 
+                        docs.path LIKE '$path/%' AND
+                        props.c_id 	= $course_id AND
+                        props.tool 	= '$tool_document' AND                            
+                        $visibility_rule  
                         $session_condition 
                 GROUP BY ref
-               ) as table1";
+            ) as table1";
     
     $result = Database::query($sql);    
     if ($result && Database::num_rows($result) != 0) {