diff --git a/Marlin/src/HAL/STM32/MarlinSerial.cpp b/Marlin/src/HAL/STM32/MarlinSerial.cpp
index 1961791e2..65ef91e31 100644
--- a/Marlin/src/HAL/STM32/MarlinSerial.cpp
+++ b/Marlin/src/HAL/STM32/MarlinSerial.cpp
@@ -26,6 +26,14 @@
   #include "../../feature/e_parser.h"
 #endif
 
+#ifndef USART4
+  #define USART4 UART4
+#endif
+
+#ifndef USART5
+  #define USART5 UART5
+#endif
+
 #define DECLARE_SERIAL_PORT(ser_num) \
   void _rx_complete_irq_ ## ser_num (serial_t * obj); \
   MarlinSerial MSerial ## ser_num (USART ## ser_num, &_rx_complete_irq_ ## ser_num); \