diff --git a/README.md b/README.md
index 19d494f..b461a79 100644
--- a/README.md
+++ b/README.md
@@ -73,6 +73,7 @@ The following status codes exists:
 * AM2302_READ_OK          {0};
 * AM2302_ERROR_CHECKSUM   {-1};
 * AM2302_ERROR_TIMEOUT    {-2};
+* AM2302_ERROR_READ_FREQ  {-3};
 
 
 # License
@@ -82,4 +83,4 @@ This library is licensed under MIT Licence.
 
 
 # Helpful Links
-* [ESP8266-01-Adapter](https://esp8266-01-adapter.de)
\ No newline at end of file
+* [ESP8266-01-Adapter](https://esp8266-01-adapter.de)