diff --git a/msi.c b/msi.c
index 73a5802..01efb4b 100644
--- a/msi.c
+++ b/msi.c
@@ -34,7 +34,7 @@ static uint32_t get_fat_sector_location(MSI_FILE *msi, uint32_t fatSectorNumber)
 	const u_char *address;
 
 	if (fatSectorNumber < DIFAT_IN_HEADER) {
-		return msi->m_hdr->headerDIFAT[fatSectorNumber];
+		return LE_UINT32(msi->m_hdr->headerDIFAT[fatSectorNumber]);
 	} else {
 		fatSectorNumber -= DIFAT_IN_HEADER;
 		entriesPerSector = msi->m_sectorSize / 4 - 1;
diff --git a/msi.h b/msi.h
index 0eb7bc1..881ed04 100644
--- a/msi.h
+++ b/msi.h
@@ -103,6 +103,40 @@
 #define SIZE_64K 65536			/* 2^16 */
 #define SIZE_16M 16777216		/* 2^24 */
 
+/*
+ * Macro names:
+ * linux:  __BYTE_ORDER == __LITTLE_ENDIAN | __BIG_ENDIAN
+ *           BYTE_ORDER == LITTLE_ENDIAN | BIG_ENDIAN
+ * bsd:     _BYTE_ORDER == _LITTLE_ENDIAN | _BIG_ENDIAN
+ *           BYTE_ORDER == LITTLE_ENDIAN | BIG_ENDIAN
+ * solaris: _LITTLE_ENDIAN | _BIG_ENDIAN
+ */
+
+#ifndef BYTE_ORDER
+#define LITTLE_ENDIAN    1234
+#define BIG_ENDIAN       4321
+#define BYTE_ORDER       LITTLE_ENDIAN
+#endif /* BYTE_ORDER */
+
+#if !defined(BYTE_ORDER) || !defined(LITTLE_ENDIAN) || !defined(BIG_ENDIAN)
+#error "Cannot determine the endian-ness of this platform"
+#endif
+
+#define LOWORD(x) (x & 0xFFFF)
+#define HIWORD(x) (x >> 16)
+
+#if BYTE_ORDER == BIG_ENDIAN
+#define LE_UINT16(x) ((((x) >> 8) & 0x00FF) | \
+                     (((x) << 8) & 0xFF00))
+#define LE_UINT32(x) (((x) >> 24) | \
+                     (((x) & 0x00FF0000) >> 8) | \
+                     (((x) & 0x0000FF00) << 8) | \
+                     ((x) << 24))
+#else
+#define LE_UINT16(x) (x)
+#define LE_UINT32(x) (x)
+#endif /* BYTE_ORDER == BIG_ENDIAN */
+
 typedef unsigned char u_char;
 
 typedef struct {
diff --git a/osslsigncode.c b/osslsigncode.c
index 7e9d00d..e4cbd52 100644
--- a/osslsigncode.c
+++ b/osslsigncode.c
@@ -1817,9 +1817,13 @@ static int set_indirect_data_blob(PKCS7 *sig, BIO *hash, file_type_t type,
 	return 1; /* OK */
 }
 
+/*
+ * A signed PE file is padded (with 0's) to 8 byte boundary.
+ * Ignore any last odd byte in an unsigned file.
+ */
 static uint32_t pe_calc_checksum(BIO *bio, FILE_HEADER *header)
 {
-	uint32_t checksum = 0, size = 0;
+	uint32_t checkSum = 0, offset = 0;
 	int nread;
 	unsigned short *buf = OPENSSL_malloc(SIZE_64K);
 
@@ -1829,18 +1833,18 @@ static uint32_t pe_calc_checksum(BIO *bio, FILE_HEADER *header)
 		unsigned short val;
 		int i;
 		for (i = 0; i < nread / 2; i++) {
-			val = buf[i];
-			if (size == header->header_size + 88 || size == header->header_size + 90)
+			val = LE_UINT16(buf[i]);
+			if (offset == header->header_size + 88 || offset == header->header_size + 90)
 				val = 0;
-			checksum += val;
-			checksum = 0xffff & (checksum + (checksum >> 0x10));
-			size += 2;
+			checkSum += val;
+			checkSum = LOWORD(LOWORD(checkSum) + HIWORD(checkSum));
+			offset += 2;
 		}
 	}
 	OPENSSL_free(buf);
-	checksum = 0xffff & (checksum + (checksum >> 0x10));
-	checksum += size;
-	return checksum;
+	checkSum = LOWORD(LOWORD(checkSum) + HIWORD(checkSum));
+	checkSum += offset;
+	return checkSum;
 }
 
 static void pe_recalc_checksum(BIO *bio, FILE_HEADER *header)