diff --git a/cmsis/stm32f4xx.h b/cmsis/stm32f4xx.h
index ed2de13..4cd837a 100644
--- a/cmsis/stm32f4xx.h
+++ b/cmsis/stm32f4xx.h
@@ -97,7 +97,7 @@
   */           
 
 #if !defined  (HSE_VALUE) 
-  #define HSE_VALUE    ((uint32_t)25000000) /*!< Value of the External oscillator in Hz */
+  #define HSE_VALUE    ((uint32_t)12000000) /*!< Value of the External oscillator in Hz */
 #endif /* HSE_VALUE */
 
 /**
diff --git a/cmsis/system_stm32f4xx.c b/cmsis/system_stm32f4xx.c
index 65a0060..6a0ca12 100644
--- a/cmsis/system_stm32f4xx.c
+++ b/cmsis/system_stm32f4xx.c
@@ -152,7 +152,7 @@
 
 /************************* PLL Parameters *************************************/
 /* PLL_VCO = (HSE_VALUE or HSI_VALUE / PLL_M) * PLL_N */
-#define PLL_M      25
+#define PLL_M      12
 #define PLL_N      336
 
 /* SYSCLK = PLL_VCO / PLL_P */