diff --git a/www/admin/table_arrays/array_edit_users.inc b/www/admin/table_arrays/array_edit_users.inc
index c9b86a9a..1f0cd95e 100644
--- a/www/admin/table_arrays/array_edit_users.inc
+++ b/www/admin/table_arrays/array_edit_users.inc
@@ -34,6 +34,7 @@
 				'output_name' => 'Password change interval',
 				'error_check' => 'intervalshort', // can be any date length format. n Y/M/D [not H/M/S], only one set, no combination
 				'type' => 'text',
+				'interval' => 1, // interval needs NULL write for empty
 				'size' => 5, // make it 5 chars long
 				'length' => 5
 			),
diff --git a/www/libs/Class.DB.Array.IO.inc b/www/libs/Class.DB.Array.IO.inc
index 00aacd4e..2faa225a 100644
--- a/www/libs/Class.DB.Array.IO.inc
+++ b/www/libs/Class.DB.Array.IO.inc
@@ -429,6 +429,13 @@ $this->debug('write_check', "[$column][".$this->table_array[$column]["value"]."]
 							$_value = $this->table_array[$column]["value"];
 						$q_data .= $_value;
 					}
+					elseif ($this->table_array[$column]["interval"])
+					{
+						// for interval we check if no value, then we set null
+						if (!$this->table_array[$column]["value"])
+							$_value = 'NULL';
+						$q_data .= $_value;
+					}
 					else
 					// normal string
 					{
@@ -500,7 +507,10 @@ $this->debug('write_check', "[$column][".$this->table_array[$column]["value"]."]
 			} 
 			// set primary key
 			if ($insert)
-				$this->ok = $this->table_array[$this->pk_name]["value"] = $this->insert_id;
+			{
+				$this->table_array[$this->pk_name]["value"] = $this->insert_id;
+				$this->ok = $this->insert_id;
+			}
 			// return the table if needed
 			return $this->table_array;
 		}