diff --git a/arduino/libretuya/api/SoftwareSerial.cpp b/arduino/libretuya/api/SoftwareSerial.cpp
index 9094b8c..00ad31d 100644
--- a/arduino/libretuya/api/SoftwareSerial.cpp
+++ b/arduino/libretuya/api/SoftwareSerial.cpp
@@ -2,6 +2,8 @@
 
 #include "SoftwareSerial.h"
 
+#ifdef LT_ARD_HAS_SOFTSERIAL
+
 SoftwareSerial::SoftwareSerial(pin_size_t receivePin, pin_size_t transmitPin, bool inverted) {
 	data.rx.buf = NULL;
 	data.tx.buf = NULL;
@@ -39,3 +41,5 @@ size_t SoftwareSerial::write(uint8_t c) {
 	}
 	return 1;
 }
+
+#endif
diff --git a/arduino/libretuya/api/SoftwareSerial.h b/arduino/libretuya/api/SoftwareSerial.h
index 0d21d43..5bcafda 100644
--- a/arduino/libretuya/api/SoftwareSerial.h
+++ b/arduino/libretuya/api/SoftwareSerial.h
@@ -2,6 +2,8 @@
 
 #pragma once
 
+#ifdef LT_ARD_HAS_SOFTSERIAL
+
 #include <Arduino.h>
 #include <api/HardwareSerial.h>
 #include <api/RingBuffer.h>
@@ -71,4 +73,4 @@ class SoftwareSerial : public HardwareSerial {
 	using Print::write;
 };
 
-#define HAS_SERIAL_CLASS 1
+#endif
diff --git a/builder/frameworks/realtek-ambz-arduino.py b/builder/frameworks/realtek-ambz-arduino.py
index 4135b4b..ba6d369 100644
--- a/builder/frameworks/realtek-ambz-arduino.py
+++ b/builder/frameworks/realtek-ambz-arduino.py
@@ -27,6 +27,7 @@ env.Append(
         # LibreTuya configuration
         ("LT_ARD_HAS_WIFI", "1"),
         ("LT_ARD_HAS_MD5", "1"),
+        ("LT_ARD_HAS_SOFTSERIAL", "1"),
         # not broken anymore with printf() library
         ("LT_PRINTF_BROKEN", "0"),
     ],
diff --git a/docs/reference/config.md b/docs/reference/config.md
index f0bb39f..44fd4d3 100644
--- a/docs/reference/config.md
+++ b/docs/reference/config.md
@@ -112,4 +112,5 @@ The meaning of most flags is as follows:
 - `LT_HAS_MBEDTLS` - mbedTLS in SDK
 - `LT_ARD_HAS_MD5` - MD5 library implemented, `MD5Impl.h` available
 - `LT_ARD_HAS_WIFI` - WiFi library implemented, `WiFiData.h` available
+- `LT_ARD_HAS_SOFTSERIAL` - SoftwareSerial library implemented, `SoftwareSerial.h` available
 - `LT_HEAP_FUNC` - function name used to get available heap size (for `LT_HEAP_I()`)