diff --git a/include/esp32-lora.h b/include/esp32-lora.h
index 0037b06..20f0b23 100644
--- a/include/esp32-lora.h
+++ b/include/esp32-lora.h
@@ -29,6 +29,7 @@
 #define REG_PREAMBLE_MSB         0x20
 #define REG_PREAMBLE_LSB         0x21
 #define REG_PAYLOAD_LENGTH       0x22
+#define REG_HOP_PERIOD           0x24
 #define REG_MODEM_CONFIG_3       0x26
 #define REG_RSSI_WIDEBAND        0x2c
 #define REG_DETECTION_OPTIMIZE   0x31