diff --git a/htdocs/application/controllers/Main.php b/htdocs/application/controllers/Main.php
index 6cd43fe..1b8581f 100644
--- a/htdocs/application/controllers/Main.php
+++ b/htdocs/application/controllers/Main.php
@@ -312,18 +312,25 @@ class Main extends CI_Controller
 
 		//upgrade to CI 3.1.2
 		$fields = $this->db->field_data('sessions');
-		
-		if ($field->max_length < 128) 
+		foreach ($fields as $field) 
 		{
-			$db_prefix = config_item('db_prefix');
 			
-			if ($this->db->dbdriver == "postgre") 
+			if ($field->name == 'id') 
 			{
-				$this->db->query("ALTER TABLE " . $db_prefix . "sessions ALTER COLUMN id SET DATA TYPE varchar(128)");
-			}
-			else
-			{
-				$this->db->query("ALTER TABLE " . $db_prefix . "sessions CHANGE id id VARCHAR(128) NOT NULL");
+				
+				if ($field->max_length < 128) 
+				{
+					$db_prefix = config_item('db_prefix');
+					
+					if ($this->db->dbdriver == "postgre") 
+					{
+						$this->db->query("ALTER TABLE " . $db_prefix . "sessions ALTER COLUMN id SET DATA TYPE varchar(128)");
+					}
+					else
+					{
+						$this->db->query("ALTER TABLE " . $db_prefix . "sessions CHANGE id id VARCHAR(128) NOT NULL");
+					}
+				}
 			}
 		}
 	}