diff --git a/cores/arduino/stm32/stm32_def.h b/cores/arduino/stm32/stm32_def.h
index f922d383cf..d0352ce727 100644
--- a/cores/arduino/stm32/stm32_def.h
+++ b/cores/arduino/stm32/stm32_def.h
@@ -20,7 +20,6 @@
                                         |(STM32_CORE_VERSION_PATCH << 8U )\
                                         |(STM32_CORE_VERSION_EXTRA))
 
-#define F_CPU SystemCoreClock
 #define USE_HAL_DRIVER
 
 #ifdef STM32F0xx
@@ -53,6 +52,10 @@
 #error "STM32YYxx chip series is not defined in boards.txt."
 #endif
 
+#ifndef F_CPU
+#define F_CPU SystemCoreClock
+#endif
+
 // Here define some compatibility
 #ifndef CAN1
 #define CAN1 CAN