diff --git a/arch/arm/cpu/armv7m/stm32f4/flash.c b/arch/arm/cpu/armv7m/stm32f4/flash.c
index ae63790..dd058bd 100644
--- a/arch/arm/cpu/armv7m/stm32f4/flash.c
+++ b/arch/arm/cpu/armv7m/stm32f4/flash.c
@@ -97,6 +97,9 @@ int flash_erase(flash_info_t *info, int first, int last)
 		while (readl(&STM32_FLASH->sr) & STM32_FLASH_SR_BSY)
 			;
 
+		/* clear old sector number before writing a new one */
+		clrbits_le32(&STM32_FLASH->cr, STM32_FLASH_CR_SNB_MASK);
+
 		if (bank == 0) {
 			setbits_le32(&STM32_FLASH->cr,
 				     (i << STM32_FLASH_CR_SNB_OFFSET));
diff --git a/arch/arm/include/asm/arch-stm32f4/stm32.h b/arch/arm/include/asm/arch-stm32f4/stm32.h
index 3ed3801..7ca6dc3 100644
--- a/arch/arm/include/asm/arch-stm32f4/stm32.h
+++ b/arch/arm/include/asm/arch-stm32f4/stm32.h
@@ -104,6 +104,7 @@ struct stm32_flash_regs {
 #define STM32_FLASH_CR_STRT		(1 << 16)
 #define STM32_FLASH_CR_LOCK		(1 << 31)
 #define STM32_FLASH_CR_SNB_OFFSET	3
+#define STM32_FLASH_CR_SNB_MASK		(15 << STM32_FLASH_CR_SNB_OFFSET)
 
 enum clock {
 	CLOCK_CORE,