diff --git a/Marlin/src/HAL/HAL_AVR/MarlinSerial.cpp b/Marlin/src/HAL/HAL_AVR/MarlinSerial.cpp
index ff1b6569ba..9bc224bd2b 100644
--- a/Marlin/src/HAL/HAL_AVR/MarlinSerial.cpp
+++ b/Marlin/src/HAL/HAL_AVR/MarlinSerial.cpp
@@ -739,24 +739,24 @@
 
 #endif // !USBCON && (UBRRH || UBRR0H || UBRR1H || UBRR2H || UBRR3H)
 
+#ifdef INTERNAL_SERIAL_PORT
 
-#if defined(INTERNAL_SERIAL_PORT)
+  ISR(SERIAL_REGNAME(USART,INTERNAL_SERIAL_PORT,_RX_vect)) {
+    MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>>::store_rxd_char();
+  }
 
-    ISR(SERIAL_REGNAME(USART,INTERNAL_SERIAL_PORT,_RX_vect)) {
-      MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>>::store_rxd_char();
-    }
+  ISR(SERIAL_REGNAME(USART,INTERNAL_SERIAL_PORT,_UDRE_vect)) {
+    MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>>::_tx_udr_empty_irq();
+  }
 
-    ISR(SERIAL_REGNAME(USART,INTERNAL_SERIAL_PORT,_UDRE_vect)) {
-      MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>>::_tx_udr_empty_irq();
-    }
+  // Preinstantiate
+  template class MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>>;
 
-    // Preinstantiate
-    template class MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>>;
-
-    // Instantiate
-    MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>> internalSerial;
+  // Instantiate
+  MarlinSerial<MarlinInternalSerialCfg<INTERNAL_SERIAL_PORT>> internalSerial;
 
 #endif
+
 // For AT90USB targets use the UART for BT interfacing
 #if defined(USBCON) && ENABLED(BLUETOOTH)
   HardwareSerial bluetoothSerial;
diff --git a/Marlin/src/HAL/HAL_AVR/MarlinSerial.h b/Marlin/src/HAL/HAL_AVR/MarlinSerial.h
index bd0a6234f0..5ada120c6d 100644
--- a/Marlin/src/HAL/HAL_AVR/MarlinSerial.h
+++ b/Marlin/src/HAL/HAL_AVR/MarlinSerial.h
@@ -276,7 +276,7 @@
 #endif // !USBCON
 
 
-#if defined(INTERNAL_SERIAL_PORT)
+#ifdef INTERNAL_SERIAL_PORT
   template <uint8_t serial>
   struct MarlinInternalSerialCfg {
     static constexpr int PORT               = serial;
diff --git a/Marlin/src/lcd/dogm/HAL_LCD_com_defines.h b/Marlin/src/lcd/dogm/HAL_LCD_com_defines.h
index 0785cb79a6..79f7f2f358 100644
--- a/Marlin/src/lcd/dogm/HAL_LCD_com_defines.h
+++ b/Marlin/src/lcd/dogm/HAL_LCD_com_defines.h
@@ -47,7 +47,7 @@
   uint8_t u8g_com_HAL_LPC1768_ssd_hw_i2c_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_val, void *arg_ptr);
   #define U8G_COM_SSD_I2C_HAL u8g_com_arduino_ssd_i2c_fn
 
-  #if defined(ARDUINO_ARCH_STM32F1)
+  #ifdef ARDUINO_ARCH_STM32F1
     uint8_t u8g_com_stm32duino_fsmc_fn(u8g_t *u8g, uint8_t msg, uint8_t arg_val, void *arg_ptr);
     #define U8G_COM_HAL_FSMC_FN u8g_com_stm32duino_fsmc_fn
   #else