diff --git a/src/checksum.c b/src/checksum.c
index 9d06630..6dcdcd5 100644
--- a/src/checksum.c
+++ b/src/checksum.c
@@ -69,7 +69,7 @@ checksum_xor_uint8 (const unsigned char data[], unsigned int size, unsigned char
 
 
 unsigned short
-checksum_crc16_ccitt (const unsigned char data[], unsigned int size, unsigned short init)
+checksum_crc16_ccitt (const unsigned char data[], unsigned int size, unsigned short init, unsigned short xorout)
 {
 	static const unsigned short crc_ccitt_table[] = {
 		0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
@@ -110,7 +110,7 @@ checksum_crc16_ccitt (const unsigned char data[], unsigned int size, unsigned sh
 	for (unsigned int i = 0; i < size; ++i)
 		crc = (crc << 8) ^ crc_ccitt_table[(crc >> 8) ^ data[i]];
 
-	return crc;
+	return crc ^ xorout;
 }
 
 unsigned int
diff --git a/src/checksum.h b/src/checksum.h
index c8a9001..39da07c 100644
--- a/src/checksum.h
+++ b/src/checksum.h
@@ -39,7 +39,7 @@ unsigned char
 checksum_xor_uint8 (const unsigned char data[], unsigned int size, unsigned char init);
 
 unsigned short
-checksum_crc16_ccitt (const unsigned char data[], unsigned int size, unsigned short init);
+checksum_crc16_ccitt (const unsigned char data[], unsigned int size, unsigned short init, unsigned short xorout);
 
 unsigned int
 checksum_crc32 (const unsigned char data[], unsigned int size);
diff --git a/src/cressi_goa.c b/src/cressi_goa.c
index e414743..9df10e8 100644
--- a/src/cressi_goa.c
+++ b/src/cressi_goa.c
@@ -93,7 +93,7 @@ cressi_goa_device_send (cressi_goa_device_t *device, unsigned char cmd, const un
 	if (size) {
 		memcpy (packet + 5, data, size);
 	}
-	crc = checksum_crc16_ccitt (packet + 3, size + 2, 0x000);
+	crc = checksum_crc16_ccitt (packet + 3, size + 2, 0x000, 0x0000);
 	packet[5 + size + 0] = (crc     ) & 0xFF; // Low
 	packet[5 + size + 1] = (crc >> 8) & 0xFF; // High
 	packet[5 + size + 2] = TRAILER;
@@ -155,7 +155,7 @@ cressi_goa_device_receive (cressi_goa_device_t *device, unsigned char data[], un
 
 	// Verify the checksum of the packet.
 	unsigned short crc = array_uint16_le (packet + length + 5);
-	unsigned short ccrc = checksum_crc16_ccitt (packet + 3, length + 2, 0x0000);
+	unsigned short ccrc = checksum_crc16_ccitt (packet + 3, length + 2, 0x0000, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected answer checksum.");
 		return DC_STATUS_PROTOCOL;
@@ -203,7 +203,7 @@ cressi_goa_device_download (cressi_goa_device_t *device, dc_buffer_t *buffer, dc
 
 		// Verify the checksum of the packet.
 		unsigned short crc = array_uint16_le (packet + sizeof(packet) - 2);
-		unsigned short ccrc = checksum_crc16_ccitt (packet + 3, sizeof(packet) - 5, 0x0000);
+		unsigned short ccrc = checksum_crc16_ccitt (packet + 3, sizeof(packet) - 5, 0x0000, 0x0000);
 		if (crc != ccrc) {
 			ERROR (abstract->context, "Unexpected answer checksum.");
 			return DC_STATUS_PROTOCOL;
diff --git a/src/cressi_leonardo.c b/src/cressi_leonardo.c
index f331537..dd941da 100644
--- a/src/cressi_leonardo.c
+++ b/src/cressi_leonardo.c
@@ -84,7 +84,7 @@ cressi_leonardo_make_ascii (const unsigned char raw[], unsigned int rsize, unsig
 	array_convert_bin2hex (raw, rsize, ascii + 1, 2 * rsize);
 
 	// Checksum
-	unsigned short crc = checksum_crc16_ccitt (ascii + 1, 2 * rsize, 0xffff);
+	unsigned short crc = checksum_crc16_ccitt (ascii + 1, 2 * rsize, 0xffff, 0x0000);
 	unsigned char checksum[] = {
 			(crc >> 8) & 0xFF,  // High
 			(crc     ) & 0xFF}; // Low
@@ -129,7 +129,7 @@ cressi_leonardo_packet (cressi_leonardo_device_t *device, const unsigned char co
 
 	// Verify the checksum of the packet.
 	unsigned short crc = array_uint16_be (checksum);
-	unsigned short ccrc = checksum_crc16_ccitt (answer + 1, asize - 6, 0xffff);
+	unsigned short ccrc = checksum_crc16_ccitt (answer + 1, asize - 6, 0xffff, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected answer checksum.");
 		return DC_STATUS_PROTOCOL;
@@ -372,7 +372,7 @@ cressi_leonardo_device_dump (dc_device_t *abstract, dc_buffer_t *buffer)
 
 	// Verify the checksum.
 	unsigned int csum1 = array_uint16_be (checksum);
-	unsigned int csum2 = checksum_crc16_ccitt (data, SZ_MEMORY, 0xffff);
+	unsigned int csum2 = checksum_crc16_ccitt (data, SZ_MEMORY, 0xffff, 0x0000);
 	if (csum1 != csum2) {
 		ERROR (abstract->context, "Unexpected answer bytes.");
 		return DC_STATUS_PROTOCOL;
diff --git a/src/divesystem_idive.c b/src/divesystem_idive.c
index 0410cd2..4a0bca3 100644
--- a/src/divesystem_idive.c
+++ b/src/divesystem_idive.c
@@ -231,7 +231,7 @@ divesystem_idive_send (divesystem_idive_device_t *device, const unsigned char co
 	packet[0] = START;
 	packet[1] = csize;
 	memcpy(packet + 2, command, csize);
-	crc = checksum_crc16_ccitt (packet, csize + 2, 0xffff);
+	crc = checksum_crc16_ccitt (packet, csize + 2, 0xffff, 0x0000);
 	packet[csize + 2] = (crc >> 8) & 0xFF;
 	packet[csize + 3] = (crc     ) & 0xFF;
 
@@ -292,7 +292,7 @@ divesystem_idive_receive (divesystem_idive_device_t *device, unsigned char answe
 
 	// Verify the checksum.
 	unsigned short crc = array_uint16_be (packet + len + 2);
-	unsigned short ccrc = checksum_crc16_ccitt (packet, len + 2, 0xffff);
+	unsigned short ccrc = checksum_crc16_ccitt (packet, len + 2, 0xffff, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected packet checksum.");
 		return DC_STATUS_PROTOCOL;
diff --git a/src/liquivision_lynx.c b/src/liquivision_lynx.c
index a0d8e0a..e7ad5a4 100644
--- a/src/liquivision_lynx.c
+++ b/src/liquivision_lynx.c
@@ -158,7 +158,7 @@ liquivision_lynx_recv (liquivision_lynx_device_t *device, unsigned char data[],
 
 	// Verify the checksum.
 	unsigned short crc = array_uint16_be (packet + 1 + size);
-	unsigned short ccrc = checksum_crc16_ccitt (packet + 1, size, 0xffff);
+	unsigned short ccrc = checksum_crc16_ccitt (packet + 1, size, 0xffff, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected answer checksum (%04x %04x).", crc, ccrc);
 		return DC_STATUS_PROTOCOL;
diff --git a/src/mares_iconhd_parser.c b/src/mares_iconhd_parser.c
index 184bf92..600eaa9 100644
--- a/src/mares_iconhd_parser.c
+++ b/src/mares_iconhd_parser.c
@@ -296,7 +296,7 @@ mares_genius_isvalid (const unsigned char data[], size_t size, unsigned int type
 	}
 
 	unsigned short crc = array_uint16_le(data + size - 6);
-	unsigned short ccrc = checksum_crc16_ccitt(data + 4, size - 10, 0x0000);
+	unsigned short ccrc = checksum_crc16_ccitt(data + 4, size - 10, 0x0000, 0x0000);
 	if (crc != ccrc) {
 		return 0;
 	}
diff --git a/src/oceans_s1.c b/src/oceans_s1.c
index e26979e..125d090 100644
--- a/src/oceans_s1.c
+++ b/src/oceans_s1.c
@@ -302,7 +302,7 @@ oceans_s1_xmodem_packet (oceans_s1_device_t *device, unsigned char seq, unsigned
 	}
 
 	unsigned short crc = array_uint16_be (packet + nbytes - 2);
-	unsigned short ccrc = checksum_crc16_ccitt (packet + 3, nbytes - 5, 0x0000);
+	unsigned short ccrc = checksum_crc16_ccitt (packet + 3, nbytes - 5, 0x0000, 0x0000);
 	if (crc != ccrc) {
 		ERROR (device->base.context, "Unexpected answer checksum (%04x %04x).", crc, ccrc);
 		return DC_STATUS_PROTOCOL;
diff --git a/src/reefnet_sensuspro.c b/src/reefnet_sensuspro.c
index 835fbcb..27c2fdb 100644
--- a/src/reefnet_sensuspro.c
+++ b/src/reefnet_sensuspro.c
@@ -177,7 +177,7 @@ reefnet_sensuspro_handshake (reefnet_sensuspro_device_t *device)
 
 	// Verify the checksum of the handshake packet.
 	unsigned short crc = array_uint16_le (handshake + SZ_HANDSHAKE);
-	unsigned short ccrc = checksum_crc16_ccitt (handshake, SZ_HANDSHAKE, 0xffff);
+	unsigned short ccrc = checksum_crc16_ccitt (handshake, SZ_HANDSHAKE, 0xffff, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected answer checksum.");
 		return DC_STATUS_PROTOCOL;
@@ -280,7 +280,7 @@ reefnet_sensuspro_device_dump (dc_device_t *abstract, dc_buffer_t *buffer)
 	}
 
 	unsigned short crc = array_uint16_le (answer + SZ_MEMORY);
-	unsigned short ccrc = checksum_crc16_ccitt (answer, SZ_MEMORY, 0xffff);
+	unsigned short ccrc = checksum_crc16_ccitt (answer, SZ_MEMORY, 0xffff, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected answer checksum.");
 		return DC_STATUS_PROTOCOL;
diff --git a/src/reefnet_sensusultra.c b/src/reefnet_sensusultra.c
index 6b059d6..bfe1c6a 100644
--- a/src/reefnet_sensusultra.c
+++ b/src/reefnet_sensusultra.c
@@ -224,7 +224,7 @@ reefnet_sensusultra_packet (reefnet_sensusultra_device_t *device, unsigned char
 
 	// Verify the checksum of the packet.
 	unsigned short crc = array_uint16_le (data + size - 2);
-	unsigned short ccrc = checksum_crc16_ccitt (data + header, size - header - 2, 0xffff);
+	unsigned short ccrc = checksum_crc16_ccitt (data + header, size - header - 2, 0xffff, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected answer checksum.");
 		return DC_STATUS_PROTOCOL;
@@ -477,7 +477,7 @@ reefnet_sensusultra_device_write_user (dc_device_t *abstract, const unsigned cha
 	}
 
 	// Send the checksum to the device.
-	unsigned short crc = checksum_crc16_ccitt (data, SZ_USER, 0xffff);
+	unsigned short crc = checksum_crc16_ccitt (data, SZ_USER, 0xffff, 0x0000);
 	rc = reefnet_sensusultra_send_ushort (device, crc);
 	if (rc != DC_STATUS_SUCCESS)
 		return rc;
diff --git a/src/seac_screen.c b/src/seac_screen.c
index e9b5366..9b3796f 100644
--- a/src/seac_screen.c
+++ b/src/seac_screen.c
@@ -115,7 +115,7 @@ seac_screen_send (seac_screen_device_t *device, unsigned short cmd, const unsign
 	if (size) {
 		memcpy (packet + 5, data, size);
 	}
-	crc = checksum_crc16_ccitt (packet, size + 5, 0xFFFF);
+	crc = checksum_crc16_ccitt (packet, size + 5, 0xFFFF, 0x0000);
 	packet[size +  5] = (crc >> 8) & 0xFF;
 	packet[size +  6] = (crc     ) & 0xFF;
 
@@ -165,7 +165,7 @@ seac_screen_receive (seac_screen_device_t *device, unsigned short cmd, unsigned
 
 	// Verify the checksum.
 	unsigned short crc = array_uint16_be (packet + 1 + length - 2);
-	unsigned short ccrc = checksum_crc16_ccitt (packet, 1 + length - 2, 0xFFFF);
+	unsigned short ccrc = checksum_crc16_ccitt (packet, 1 + length - 2, 0xFFFF, 0x0000);
 	if (crc != ccrc) {
 		ERROR (abstract->context, "Unexpected packet checksum (%04x %04x).", crc, ccrc);
 		return DC_STATUS_PROTOCOL;
@@ -486,8 +486,8 @@ seac_screen_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback,
 		device_event_emit (abstract, DC_EVENT_PROGRESS, &progress);
 
 		// Check the header checksums.
-		if (checksum_crc16_ccitt (logbook[i].header, SZ_HEADER / 2, 0xFFFF) != 0 ||
-			checksum_crc16_ccitt (logbook[i].header + SZ_HEADER / 2, SZ_HEADER / 2, 0xFFFF) != 0) {
+		if (checksum_crc16_ccitt (logbook[i].header, SZ_HEADER / 2, 0xFFFF, 0x0000) != 0 ||
+			checksum_crc16_ccitt (logbook[i].header + SZ_HEADER / 2, SZ_HEADER / 2, 0xFFFF, 0x0000) != 0) {
 			ERROR (abstract->context, "Unexpected header checksum.");
 			status = DC_STATUS_DATAFORMAT;
 			goto error_free_logbook;
diff --git a/src/seac_screen_parser.c b/src/seac_screen_parser.c
index 8c588d2..c4a855c 100644
--- a/src/seac_screen_parser.c
+++ b/src/seac_screen_parser.c
@@ -283,8 +283,8 @@ seac_screen_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_t
 	if (abstract->size < SZ_HEADER)
 		return DC_STATUS_DATAFORMAT;
 
-	if (checksum_crc16_ccitt (data, SZ_HEADER / 2, 0xFFFF) != 0 ||
-		checksum_crc16_ccitt (data + SZ_HEADER / 2, SZ_HEADER / 2, 0xFFFF) != 0) {
+	if (checksum_crc16_ccitt (data, SZ_HEADER / 2, 0xFFFF, 0x0000) != 0 ||
+		checksum_crc16_ccitt (data + SZ_HEADER / 2, SZ_HEADER / 2, 0xFFFF, 0x0000) != 0) {
 		ERROR (abstract->context, "Unexpected header checksum.");
 		return DC_STATUS_DATAFORMAT;
 	}
@@ -303,7 +303,7 @@ seac_screen_parser_samples_foreach (dc_parser_t *abstract, dc_sample_callback_t
 	while (offset + SZ_SAMPLE <= size) {
 		dc_sample_value_t sample = {0};
 
-		if (checksum_crc16_ccitt (data + offset, SZ_SAMPLE, 0xFFFF) != 0) {
+		if (checksum_crc16_ccitt (data + offset, SZ_SAMPLE, 0xFFFF, 0x0000) != 0) {
 			ERROR (abstract->context, "Unexpected sample checksum.");
 			return DC_STATUS_DATAFORMAT;
 		}