diff --git a/include/libopencm3/stm32/common/flash_common_f24.h b/include/libopencm3/stm32/common/flash_common_f24.h
index 6e61f3cb..2a762a30 100644
--- a/include/libopencm3/stm32/common/flash_common_f24.h
+++ b/include/libopencm3/stm32/common/flash_common_f24.h
@@ -138,7 +138,7 @@ void flash_clear_status_flags(void);
 void flash_unlock_option_bytes(void);
 void flash_lock_option_bytes(void);
 void flash_erase_all_sectors(u32 program_size);
-void flash_erase_sector(u32 sector, u32 program_size);
+void flash_erase_sector(u8 sector, u32 program_size);
 void flash_program_double_word(u32 address, u64 data);
 void flash_program_word(u32 address, u32 data);
 void flash_program_half_word(u32 address, u16 data);
diff --git a/lib/stm32/common/flash_common_f24.c b/lib/stm32/common/flash_common_f24.c
index f3a37716..6abff49d 100644
--- a/lib/stm32/common/flash_common_f24.c
+++ b/lib/stm32/common/flash_common_f24.c
@@ -218,19 +218,19 @@ void flash_program_byte(u32 address, u8 data)
 	FLASH_CR &= ~FLASH_CR_PG;		/* Disable the PG bit. */
 }
 
-void flash_erase_sector(u32 sector, u32 program_size)
+void flash_erase_sector(u8 sector, u32 program_size)
 {
 	flash_wait_for_last_operation();
 	flash_set_program_size(program_size);
 
-	FLASH_CR &= ~(((1 << 0) | (1 << 1) | (1 << 2) | (1 << 3)) << 3);
-	FLASH_CR |= sector;
+	FLASH_CR &= ~(0xF << 3);
+	FLASH_CR |= (sector << 3) & 0x78;
 	FLASH_CR |= FLASH_CR_SER;
 	FLASH_CR |= FLASH_CR_STRT;
 
 	flash_wait_for_last_operation();
 	FLASH_CR &= ~FLASH_CR_SER;
-	FLASH_CR &= ~(((1 << 0) | (1 << 1) | (1 << 2) | (1 << 3)) << 3);
+	FLASH_CR &= ~(0xF << 3);
 }
 
 void flash_erase_all_sectors(u32 program_size)