diff --git a/arch/arm/src/stm32l4/hardware/stm32l4_memorymap.h b/arch/arm/src/stm32l4/hardware/stm32l4_memorymap.h
index 3b1631ad487..66c669aed35 100644
--- a/arch/arm/src/stm32l4/hardware/stm32l4_memorymap.h
+++ b/arch/arm/src/stm32l4/hardware/stm32l4_memorymap.h
@@ -68,6 +68,7 @@
                                               /* 0x00100000-0x07ffffff: Reserved */
 #define STM32L4_FLASH_BASE     0x08000000     /* 0x08000000-0x080fffff: FLASH memory */
                                               /* 0x08100000-0x0fffffff: Reserved */
+#define STM32L4_FLASH_MASK     0xf8000000     /*                        Test if addr in FLASH */
 #define STM32L4_SRAM2_BASE     0x10000000     /* 0x10000000-0x1000ffff: 16k to 64k SRAM2 */
                                               /* 0x10010000-0x1ffeffff: Reserved */
 #define STM32L4_SRAM3_BASE     0x20040000     /* 0x20040000-0x3fffffff: SRAM3 (STM32L4R9xx only, 384k) */
diff --git a/arch/arm/src/stm32l4/stm32l4_firewall.c b/arch/arm/src/stm32l4/stm32l4_firewall.c
index 30378c858f4..392d6f13540 100644
--- a/arch/arm/src/stm32l4/stm32l4_firewall.c
+++ b/arch/arm/src/stm32l4/stm32l4_firewall.c
@@ -56,7 +56,7 @@ int stm32l4_firewallsetup(FAR struct stm32l4_firewall_t *setup)
 {
   uint32_t reg;
 
-  /* code and nvdata must be aligned to 256 bytes
+  /* Code and nvdata must be aligned to 256 bytes
    * data must be aligned to 64 bytes
    */
 
@@ -66,7 +66,7 @@ int stm32l4_firewallsetup(FAR struct stm32l4_firewall_t *setup)
       return -EINVAL;
     }
 
-  /* code and nvdata length must be a multiple of 256 bytes
+  /* Code and nvdata length must be a multiple of 256 bytes
    * data length must be a multiple of 64 bytes
    */
 
@@ -76,16 +76,16 @@ int stm32l4_firewallsetup(FAR struct stm32l4_firewall_t *setup)
       return -EINVAL;
     }
 
-  /* code and nvdata must be in flash
+  /* Code and nvdata must be in flash
    * data must be in SRAM1
    */
 
-  if ((setup->codestart & STM32L4_REGION_MASK) != STM32L4_FLASH_BASE)
+  if ((setup->codestart & STM32L4_FLASH_MASK) != STM32L4_FLASH_BASE)
     {
       return -EINVAL;
     }
 
-  if ((setup->nvdatastart & STM32L4_REGION_MASK) != STM32L4_FLASH_BASE)
+  if ((setup->nvdatastart & STM32L4_FLASH_MASK) != STM32L4_FLASH_BASE)
     {
       return -EINVAL;
     }