diff --git a/arch/northstar/decoder.cc b/arch/northstar/decoder.cc
index 85b4a7b0..98b8c36b 100644
--- a/arch/northstar/decoder.cc
+++ b/arch/northstar/decoder.cc
@@ -127,9 +127,9 @@ public:
 	void decodeSectorRecord() override
 	{
 		uint64_t id = toBytes(readRawBits(64)).reader().read_be64();
-
 		unsigned recordSize, payloadSize, headerSize;
-		if (id == SECTOR_TYPE_MFM) {
+
+		if (id == MFM_ID) {
 			recordSize = NORTHSTAR_ENCODED_SECTOR_SIZE_DD;
 			payloadSize = NORTHSTAR_PAYLOAD_SIZE_DD;
 			headerSize = NORTHSTAR_HEADER_SIZE_DD;
@@ -143,22 +143,18 @@ public:
 		auto rawbits = readRawBits(recordSize * 16);
 		auto bytes = decodeFmMfm(rawbits).slice(0, recordSize);
 		ByteReader br(bytes);
-		uint8_t sync_char;
 
 		_sector->logicalSide = _sector->physicalHead;
 		_sector->logicalSector = _hardSectorId;
 		_sector->logicalTrack = _sector->physicalCylinder;
 
-		sync_char = br.read_8();	/* Sync char: 0xFB */
-		if (_sectorType == SECTOR_TYPE_MFM) {
-			sync_char = br.read_8();/* MFM second Sync char, usually 0xFB */
+		if (headerSize == NORTHSTAR_HEADER_SIZE_DD) {
+			br.read_8();	/* MFM second Sync char, usually 0xFB */
 		}
 
 		_sector->data = br.read(payloadSize);
-
 		uint8_t wantChecksum = br.read_8();
-		uint8_t gotChecksum = northstarChecksum(bytes.slice(headerSize, payloadSize));
-
+		uint8_t gotChecksum = northstarChecksum(bytes.slice(headerSize - 1, payloadSize));
 		_sector->status = (wantChecksum == gotChecksum) ? Sector::OK : Sector::BAD_CHECKSUM;
 	}
 
@@ -170,7 +166,6 @@ public:
 
 private:
 	const NorthstarDecoderProto& _config;
-	uint8_t _sectorType = SECTOR_TYPE_MFM;
 	uint8_t _hardSectorId;
 };
 
diff --git a/arch/northstar/northstar.h b/arch/northstar/northstar.h
index c20a084e..2bcfdce3 100644
--- a/arch/northstar/northstar.h
+++ b/arch/northstar/northstar.h
@@ -22,9 +22,6 @@
 #define NORTHSTAR_ENCODED_SECTOR_SIZE_SD	(NORTHSTAR_HEADER_SIZE_SD + NORTHSTAR_PAYLOAD_SIZE_SD + NORTHSTAR_CHECKSUM_SIZE)
 #define NORTHSTAR_ENCODED_SECTOR_SIZE_DD	(NORTHSTAR_HEADER_SIZE_DD + NORTHSTAR_PAYLOAD_SIZE_DD + NORTHSTAR_CHECKSUM_SIZE)
 
-#define SECTOR_TYPE_MFM			(0)
-#define SECTOR_TYPE_FM				(1)
-
 class AbstractDecoder;
 class AbstractEncoder;
 class EncoderProto;