diff --git a/disk/part_efi.c b/disk/part_efi.c
index 72e3997..5c1039f 100644
--- a/disk/part_efi.c
+++ b/disk/part_efi.c
@@ -350,8 +350,6 @@ static int set_protective_mbr(struct blk_desc *dev_desc)
 {
 	/* Setup the Protective MBR */
 	ALLOC_CACHE_ALIGN_BUFFER_PAD(legacy_mbr, p_mbr, 1, dev_desc->blksz);
-	memset(p_mbr, 0, sizeof(*p_mbr));
-
 	if (p_mbr == NULL) {
 		printf("%s: calloc failed!\n", __func__);
 		return -1;
@@ -363,6 +361,10 @@ static int set_protective_mbr(struct blk_desc *dev_desc)
 		return -1;
 	}
 
+	/* Clear all data in MBR except of backed up boot code */
+	memset((char *)p_mbr + MSDOS_MBR_BOOT_CODE_SIZE, 0, sizeof(*p_mbr) -
+			MSDOS_MBR_BOOT_CODE_SIZE);
+
 	/* Append signature */
 	p_mbr->signature = MSDOS_MBR_SIGNATURE;
 	p_mbr->partition_record[0].sys_ind = EFI_PMBR_OSTYPE_EFI_GPT;
diff --git a/include/part_efi.h b/include/part_efi.h
index 6065c57..8525770 100644
--- a/include/part_efi.h
+++ b/include/part_efi.h
@@ -20,6 +20,7 @@
 #include <efi.h>
 
 #define MSDOS_MBR_SIGNATURE 0xAA55
+#define MSDOS_MBR_BOOT_CODE_SIZE 440
 #define EFI_PMBR_OSTYPE_EFI 0xEF
 #define EFI_PMBR_OSTYPE_EFI_GPT 0xEE
 
@@ -111,7 +112,7 @@ typedef struct _gpt_entry {
 } __packed gpt_entry;
 
 typedef struct _legacy_mbr {
-	u8 boot_code[440];
+	u8 boot_code[MSDOS_MBR_BOOT_CODE_SIZE];
 	__le32 unique_mbr_signature;
 	__le16 unknown;
 	struct partition partition_record[4];