diff --git a/Marlin/src/HAL/HAL_AVR/fastio_AVR.h b/Marlin/src/HAL/HAL_AVR/fastio_AVR.h
index 0c782988f..4c31e3b26 100644
--- a/Marlin/src/HAL/HAL_AVR/fastio_AVR.h
+++ b/Marlin/src/HAL/HAL_AVR/fastio_AVR.h
@@ -36,7 +36,7 @@
 #define AVR_ATmega1284_FAMILY (defined(__AVR_ATmega644__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__) || defined(__AVR_ATmega1284P__))
 #define AVR_ATmega2560_FAMILY (defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__))
 #define AVR_ATmega2561_FAMILY (defined(__AVR_ATmega1281__) || defined(__AVR_ATmega2561__))
-#define AVR_ATmega328_FAMILY (defined(__AVR_ATmega168__) || defined(__AVR_ATmega328__) || defined(__AVR_ATmega328p__))
+#define AVR_ATmega328_FAMILY (defined(__AVR_ATmega168__) || defined(__AVR_ATmega328__) || defined(__AVR_ATmega328P__))
 
 /**
  * Include Ports and Functions