diff --git a/API.md b/API.md
index 07c808e..0e4a8e9 100644
--- a/API.md
+++ b/API.md
@@ -166,6 +166,14 @@ float snr = LoRa.packetSnr();
 
 Returns the estimated SNR of the received packet in dB.
 
+### Packet Frequency Error
+
+```arduino
+long freqErr = LoRa.packetFrequencyError();
+```
+
+Returns the frequency error of the received packet in Hz. The frequency error is the frequency offset between the receiver centre frequency and that of an incoming LoRa signal.
+
 ### Available
 
 ```arduino