diff --git a/flash.c b/flash.c
--- a/flash.c
+++ b/flash.c
@@ -1,38 +1,31 @@
-#include "stm32f0xx_hal.h"
-#include "ssd1306.h"
-#include "stm32f0xx_hal_flash.h"
 #include "flash.h"
 
 __attribute__((__section__(".eeprom"))) uint16_t eeprom[512];
 
+#define MAGIC_NUMBER 0x0BAE
 
 static void __flash_write(therm_settings_t* tosave);
 
-
-#define EEPROM_MAGIC_INDEX 0
-#define EEPROM_MAGIC_VALUE 0xbeef
-
-
 void flash_save(therm_settings_t* tosave)
 {
     __flash_write(tosave);
 }
 
-
 void flash_restore(therm_settings_t* torestore)
 {
+	//read flash and calculate checksum
+	uint16_t checksum = MAGIC_NUMBER;
+	uint16_t i;
+    for(i = 0; i < (sizeof(therm_settings_t)/2); i++)
+	{
+		torestore->data[i] = eeprom[i];
+		checksum ^= torestore->data[i];
+	}
 
-    if(eeprom[EEPROM_MAGIC_INDEX] == EEPROM_MAGIC_VALUE)
-    {
-        for(uint8_t i = 1; i <= 20; i++) {
-            torestore->data[i] = *(eeprom+i);
-        }
-    }
-    else {
-        // load default settings
+    //if checksum doesn't match, load default settings
+    if((checksum ^ eeprom[i+1]) != 0) {
     	flash_load_defaults(torestore);
     }
-
 }
 
 void flash_load_defaults(therm_settings_t* torestore) {
@@ -43,19 +36,17 @@ void flash_load_defaults(therm_settings_
 	torestore->val.k_p = DEFAULT_K_P;
 	torestore->val.k_i = DEFAULT_K_I;
 	torestore->val.k_d = DEFAULT_K_D;
+	torestore->val.temp_offset = DEFAULT_TEMP_OFFSET;
 	torestore->val.ignore_error = DEFAULT_IGNORE_ERROR;
 	torestore->val.setpoint_brew = DEFAULT_SETPOINT_BREW;
 	torestore->val.setpoint_steam = DEFAULT_SETPOINT_STEAM;
 }
 
-
 static void __flash_write(therm_settings_t* tosave)
 {
-    // Erase mem    
+    // Erase mem
     HAL_FLASH_Unlock();
 
-    //TODO: add checksum instead of magic value
-    //TODO: change checksum to invalidate flash instead of erase?
     // Erase the FLASH pages
     FLASH_EraseInitTypeDef erase;
     erase.TypeErase = TYPEERASE_PAGES;
@@ -63,19 +54,22 @@ static void __flash_write(therm_settings
     erase.NbPages = 1;
     uint32_t SectorError = 0;
     HAL_FLASHEx_Erase(&erase, &SectorError);
-
     CLEAR_BIT(FLASH->CR, FLASH_CR_PER);
 
-    for(uint8_t i = 1; i <= (sizeof(therm_settings_t)/2); i++)
+    // write to flash and calculate the checksum
+    uint16_t checksum = MAGIC_NUMBER;
+    uint16_t i;
+    for(i = 0; i < (sizeof(therm_settings_t)/2); i++)
 	{
-    	HAL_FLASH_Program(TYPEPROGRAM_HALFWORD, (uint32_t)(eeprom + i), tosave->data[i]);
+		HAL_FLASH_Program(TYPEPROGRAM_HALFWORD, (uint32_t)&eeprom[i], tosave->data[i]);
+    	checksum ^= tosave->data[i];
 	}
 
-    HAL_FLASH_Program(TYPEPROGRAM_HALFWORD, (uint32_t)(eeprom + EEPROM_MAGIC_INDEX), EEPROM_MAGIC_VALUE);
+    // write the checksum
+    HAL_FLASH_Program(TYPEPROGRAM_HALFWORD, (uint32_t)&eeprom[i+1], checksum);
 
     HAL_FLASH_Lock();
 }
 
 
-
 // vim:softtabstop=4 shiftwidth=4 expandtab