diff --git a/cores/esp32/HardwareSerial.h b/cores/esp32/HardwareSerial.h
index 37f81f8a..5172a3c1 100644
--- a/cores/esp32/HardwareSerial.h
+++ b/cores/esp32/HardwareSerial.h
@@ -120,6 +120,7 @@ extern HardwareSerial Serial0;
 #else
 extern HardwareSerial Serial;
 #endif
+extern HardwareSerial Serial1;
 #if CONFIG_IDF_TARGET_ESP32
 extern HardwareSerial Serial2;
 #endif