diff --git a/ethermess-backend.c b/ethermess-backend.c
index d9547c3..baba23b 100644
--- a/ethermess-backend.c
+++ b/ethermess-backend.c
@@ -28,6 +28,7 @@
 #define EM_RETRANSMIT_TIME (1000 + random_byte() * 2)
 #define EM_MAX_RETRANSMIT 5
 
+// Version 0
 #define EMT_SPEAK_VERSION 0
 #define EMT_STATUS_REQUEST 1
 #define EMT_STATUS 2
@@ -272,7 +273,7 @@ void send_frame(const unsigned char *frame, size_t frame_length) {
 	}
 }
 
-void write_headers(unsigned char frame[14], const unsigned char destination_mac[6], unsigned char packet_type) {
+void write_headers(unsigned char frame[14], const unsigned char destination_mac[6], unsigned char version, unsigned char packet_type) {
 	// Destination MAC
 	memcpy(&frame[0], destination_mac, 6);
 
@@ -284,7 +285,7 @@ void write_headers(unsigned char frame[14], const unsigned char destination_mac[
 	frame[13] = 0x7a;
 
 	// Ethermess version
-	frame[14] = EM_PROTOCOL_VERSION;
+	frame[14] = version;
 
 	// Ethermess packet type
 	frame[15] = packet_type;
@@ -293,7 +294,7 @@ void write_headers(unsigned char frame[14], const unsigned char destination_mac[
 void send_speak_version(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2 + 1];
 
-	write_headers(frame, destination, EMT_SPEAK_VERSION);
+	write_headers(frame, destination, 0, EMT_SPEAK_VERSION);
 
 	// Version to speak
 	frame[16] = EM_PROTOCOL_VERSION;
@@ -304,7 +305,7 @@ void send_speak_version(const unsigned char destination[6]) {
 void send_status_request(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2];
 
-	write_headers(frame, destination, EMT_STATUS_REQUEST);
+	write_headers(frame, destination, 0, EMT_STATUS_REQUEST);
 
 	send_frame(frame, sizeof(frame));
 }
@@ -312,7 +313,7 @@ void send_status_request(const unsigned char destination[6]) {
 void send_status(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2 + 1 + 1 + own_nick_length];
 
-	write_headers(frame, destination, EMT_STATUS);
+	write_headers(frame, destination, 0, EMT_STATUS);
 
 	// Status
 	frame[16] = own_status;
@@ -329,7 +330,7 @@ void send_status(const unsigned char destination[6]) {
 void send_msgid_request(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2];
 
-	write_headers(frame, destination, EMT_MSGID_REQUEST);
+	write_headers(frame, destination, 0, EMT_MSGID_REQUEST);
 
 	send_frame(frame, sizeof(frame));
 }
@@ -337,7 +338,7 @@ void send_msgid_request(const unsigned char destination[6]) {
 void send_msgid(const unsigned char destination[6]) {
 	unsigned char frame[14 + 2 + 2];
 
-	write_headers(frame, destination, EMT_MSGID);
+	write_headers(frame, destination, 0, EMT_MSGID);
 
 	// Look up destination in the ID cache
 	ssize_t cache_index = msgid_cache_lookup(destination);
@@ -366,7 +367,7 @@ void send_msgid(const unsigned char destination[6]) {
 void send_message(void) {
 	unsigned char frame[14 + 2 + 2 + 2 + own_message_length];
 
-	write_headers(frame, own_message_destination_mac, EMT_MESSAGE);
+	write_headers(frame, own_message_destination_mac, 0, EMT_MESSAGE);
 
 	// Message ID
 	frame[16] = own_message_msgid >> 8;
@@ -385,7 +386,7 @@ void send_message(void) {
 void send_ack(const unsigned char destination[6], uint16_t msgid) {
 	unsigned char frame[14 + 2 + 2];
 
-	write_headers(frame, destination, EMT_ACK);
+	write_headers(frame, destination, 0, EMT_ACK);
 
 	// Message ID
 	frame[16] = msgid >> 8;