diff --git a/os/hal/platforms/STM32F4xx/hal_lld.h b/os/hal/platforms/STM32F4xx/hal_lld.h
index c7da5d8a9..bbfffd8ce 100644
--- a/os/hal/platforms/STM32F4xx/hal_lld.h
+++ b/os/hal/platforms/STM32F4xx/hal_lld.h
@@ -1141,9 +1141,7 @@
 #error "HSI not enabled, required by STM32_MCO1SEL"
 #endif
 
-#if (STM32_MCO2SEL == STM32_MCO2SEL_HSI) ||                                 \
-    ((STM32_MCO2SEL == STM32_MCO2SEL_PLL) &&                                \
-     (STM32_PLLSRC == STM32_PLLSRC_HSI))
+#if (STM32_MCO2SEL == STM32_MCO2SEL_PLL) && (STM32_PLLSRC == STM32_PLLSRC_HSI)
 #error "HSI not enabled, required by STM32_MCO2SEL"
 #endif
 
diff --git a/readme.txt b/readme.txt
index 5ad6ab798..5a81fc76b 100644
--- a/readme.txt
+++ b/readme.txt
@@ -89,6 +89,8 @@
 *****************************************************************************
 
 *** 2.7.0 ***
+- FIX: Fixed rong MCO2 check in STM32F4xx HAL driver (bug #447)(backported
+  to 2.4.6 and 2.6.2).
 - FIX: Fixed spurious half buffer callback in STM32 ADC drivers (bug #446)
   (backported to 2.4.6 and 2.6.2).
 - FIX: Fixed callbacks changes to the ADC high level driver (bug #445)