diff --git a/Marlin/src/HAL/DUE/MarlinSerial.cpp b/Marlin/src/HAL/DUE/MarlinSerial.cpp
index 50b84c0b1..5b333fbeb 100644
--- a/Marlin/src/HAL/DUE/MarlinSerial.cpp
+++ b/Marlin/src/HAL/DUE/MarlinSerial.cpp
@@ -476,7 +476,7 @@ void MarlinSerial<Cfg>::flushTX() {
 
 
 // If not using the USB port as serial port
-#if SERIAL_PORT >= 0
+#if defined(SERIAL_PORT) && SERIAL_PORT >= 0
   template class MarlinSerial< MarlinSerialCfg<SERIAL_PORT> >;
   MSerialT customizedSerial1(MarlinSerialCfg<SERIAL_PORT>::EMERGENCYPARSER);
 #endif
diff --git a/Marlin/src/HAL/STM32/MarlinSerial.cpp b/Marlin/src/HAL/STM32/MarlinSerial.cpp
index 132c602a0..265e8b5ab 100644
--- a/Marlin/src/HAL/STM32/MarlinSerial.cpp
+++ b/Marlin/src/HAL/STM32/MarlinSerial.cpp
@@ -37,19 +37,38 @@
   MSerialT MSerial ## ser_num (true, USART ## ser_num, &_rx_complete_irq_ ## ser_num); \
   void _rx_complete_irq_ ## ser_num (serial_t * obj) { MSerial ## ser_num ._rx_complete_irq(obj); }
 
-#define DECLARE_SERIAL_PORT_EXP(ser_num) DECLARE_SERIAL_PORT(ser_num)
-
-#if defined(SERIAL_PORT) && SERIAL_PORT >= 0
-  DECLARE_SERIAL_PORT_EXP(SERIAL_PORT)
+#if USING_HW_SERIAL1
+  DECLARE_SERIAL_PORT(1)
 #endif
-#if defined(SERIAL_PORT_2) && SERIAL_PORT_2 >= 0
-  DECLARE_SERIAL_PORT_EXP(SERIAL_PORT_2)
+#if USING_HW_SERIAL2
+  DECLARE_SERIAL_PORT(2)
 #endif
-#if defined(MMU2_SERIAL_PORT) && MMU2_SERIAL_PORT >= 0
-  DECLARE_SERIAL_PORT_EXP(MMU2_SERIAL_PORT)
+#if USING_HW_SERIAL3
+  DECLARE_SERIAL_PORT(3)
 #endif
-#if defined(LCD_SERIAL_PORT) && LCD_SERIAL_PORT >= 0
-  DECLARE_SERIAL_PORT_EXP(LCD_SERIAL_PORT)
+#if USING_HW_SERIAL4
+  DECLARE_SERIAL_PORT(4)
+#endif
+#if USING_HW_SERIAL5
+  DECLARE_SERIAL_PORT(5)
+#endif
+#if USING_HW_SERIAL6
+  DECLARE_SERIAL_PORT(6)
+#endif
+#if USING_HW_SERIAL7
+  DECLARE_SERIAL_PORT(7)
+#endif
+#if USING_HW_SERIAL8
+  DECLARE_SERIAL_PORT(8)
+#endif
+#if USING_HW_SERIAL9
+  DECLARE_SERIAL_PORT(9)
+#endif
+#if USING_HW_SERIAL10
+  DECLARE_SERIAL_PORT(10)
+#endif
+#if USING_HW_SERIALLP1
+  DECLARE_SERIAL_PORT(LP1)
 #endif
 
 void MarlinSerial::begin(unsigned long baud, uint8_t config) {
diff --git a/Marlin/src/inc/Conditionals_post.h b/Marlin/src/inc/Conditionals_post.h
index 84e9cf895..243305052 100644
--- a/Marlin/src/inc/Conditionals_post.h
+++ b/Marlin/src/inc/Conditionals_post.h
@@ -1842,13 +1842,6 @@
 // Set USING_HW_SERIALn flags for used Serial Ports
 //
 
-// ... HW_SerialX
-#define _SERIAL_ID(P) _CAT(HW_,P)
-
-// ... (HW_Serial1 == HW_SerialX || HW_Serial1 == HW_MSerialX)
-#define _TMC_UART_IS(P,N) ( _SERIAL_ID(P##_HARDWARE_SERIAL) == _SERIAL_ID(Serial##N) || _SERIAL_ID(P) == _SERIAL_ID(MSerial##N) )
-#define TMC_UART_IS(A,N) (defined(A##_HARDWARE_SERIAL) && _TMC_UART_IS(A, N))
-
 // Flag the indexed hardware serial ports in use
 #define CONF_SERIAL_IS(N) (  (defined(SERIAL_PORT)      && SERIAL_PORT == N) \
                           || (defined(SERIAL_PORT_2)    && SERIAL_PORT_2 == N) \
@@ -1856,6 +1849,7 @@
                           || (defined(LCD_SERIAL_PORT)  && LCD_SERIAL_PORT == N) )
 
 // Flag the named hardware serial ports in use
+#define TMC_UART_IS(A,N) (defined(A##_HARDWARE_SERIAL) && (CAT(HW_,A##_HARDWARE_SERIAL) == HW_Serial##N || CAT(HW_,A##_HARDWARE_SERIAL) == HW_MSerial##N))
 #define ANY_SERIAL_IS(N) (  CONF_SERIAL_IS(N) \
                          || TMC_UART_IS(X,  N) || TMC_UART_IS(Y , N) || TMC_UART_IS(Z , N) \
                          || TMC_UART_IS(X2, N) || TMC_UART_IS(Y2, N) || TMC_UART_IS(Z2, N) || TMC_UART_IS(Z3, N) || TMC_UART_IS(Z4, N) \