diff --git a/os/hal/ports/STM32/STM32L0xx/hal_lld.h b/os/hal/ports/STM32/STM32L0xx/hal_lld.h
index 7b7c0e10e..550308803 100644
--- a/os/hal/ports/STM32/STM32L0xx/hal_lld.h
+++ b/os/hal/ports/STM32/STM32L0xx/hal_lld.h
@@ -125,11 +125,11 @@
  * @name    RCC_CR register bits definitions
  * @{
  */
-#define STM32_RTCPRE_MASK       (3 << 29)   /**< RTCPRE mask.               */
-#define STM32_RTCPRE_DIV2       (0 << 29)   /**< HSE divided by 2.          */
-#define STM32_RTCPRE_DIV4       (1 << 29)   /**< HSE divided by 4.          */
-#define STM32_RTCPRE_DIV8       (2 << 29)   /**< HSE divided by 2.          */
-#define STM32_RTCPRE_DIV16      (3 << 29)   /**< HSE divided by 16.         */
+#define STM32_RTCPRE_MASK       (3 << 20)   /**< RTCPRE mask.               */
+#define STM32_RTCPRE_DIV2       (0 << 20)   /**< HSE divided by 2.          */
+#define STM32_RTCPRE_DIV4       (1 << 20)   /**< HSE divided by 4.          */
+#define STM32_RTCPRE_DIV8       (2 << 20)   /**< HSE divided by 2.          */
+#define STM32_RTCPRE_DIV16      (3 << 20)   /**< HSE divided by 16.         */
 /** @} */
 
 /**
@@ -891,7 +891,7 @@
 #elif (STM32_SW == STM32_SW_MSI)
 #define STM32_SYSCLK                STM32_MSICLK
 #elif (STM32_SW == STM32_SW_HSI16)
-#define STM32_SYSCLK                STM32_HSI16CLK
+#define STM32_SYSCLK                STM32_HSI16DIVCLK
 #elif (STM32_SW == STM32_SW_HSE)
 #define STM32_SYSCLK                STM32_HSECLK
 #elif (STM32_SW == STM32_SW_PLL)
diff --git a/readme.txt b/readme.txt
index 64891650e..9b0165163 100644
--- a/readme.txt
+++ b/readme.txt
@@ -89,6 +89,8 @@
 *****************************************************************************
 
 *** Next ***
+- HAL:  Fixed wrong bit mask in STM32L0 hal lld (bug #866)(backported to
+       17.6.1 and 16.1.9).
 - RT:  Fixed misplaced assertion in semaphores code (bug #865)(backported to
        17.6.1 and 16.1.9).
 - HAL: Fixed STM32 USBv1 fails the state check when USB_USE_WAIT is TRUE