diff --git a/README.md b/README.md
index 128bed0..79f9e18 100644
--- a/README.md
+++ b/README.md
@@ -5,3 +5,6 @@ This is a tool to help building Swagger documentations. It converts JSON request
   * Added unsafe format to integers that use more than 64 bits
 * Detects date and date-time formats according to [ISO 8601](https://xml2rfc.tools.ietf.org/public/rfc/html/rfc3339.html#anchor14)
 * Allows nested objects and arrays
+
+To-do:
+* Support for 'null' fields