diff --git a/cores/esp32/HardwareSerial.h b/cores/esp32/HardwareSerial.h
index 60d32a7c..3ff05c6b 100644
--- a/cores/esp32/HardwareSerial.h
+++ b/cores/esp32/HardwareSerial.h
@@ -116,6 +116,7 @@ extern HardwareSerial Serial0;
 #else
 extern HardwareSerial Serial;
 #endif
+extern HardwareSerial Serial1;
 #if CONFIG_IDF_TARGET_ESP32
 extern HardwareSerial Serial2;
 #endif