diff --git a/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.cpp b/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.cpp
index 5f95a1888..309500d48 100644
--- a/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.cpp
+++ b/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.cpp
@@ -28,7 +28,7 @@
 
 // Constructor
 
-SoftwareSerial::SoftwareSerial(pin_t RX_pin, pin_t TX_pin) {}
+SoftwareSerial::SoftwareSerial(int8_t RX_pin, int8_t TX_pin) {}
 
 // Public
 
diff --git a/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.h b/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.h
index 34bbb8548..0692b7e9f 100644
--- a/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.h
+++ b/Marlin/src/HAL/HAL_STM32F1/SoftwareSerial.h
@@ -18,13 +18,13 @@
  */
 #pragma once
 
-#include "HAL.h"
+#include <stdint.h>
 
 #define SW_SERIAL_PLACEHOLDER 1
 
 class SoftwareSerial {
 public:
-  SoftwareSerial(pin_t RX_pin, pin_t TX_pin);
+  SoftwareSerial(int8_t RX_pin, int8_t TX_pin);
 
   void begin(const uint32_t baudrate);