diff --git a/common/network/Udp.cxx b/common/network/Udp.cxx
index e59d0f1..9fd4dfa 100644
--- a/common/network/Udp.cxx
+++ b/common/network/Udp.cxx
@@ -40,7 +40,7 @@ using namespace network;
 static rfb::LogWriter vlog("WebUdp");
 static WuHost *host = NULL;
 
-rfb::IntParameter udpSize("udpSize", "UDP packet data size", 1300, 500, 1400);
+rfb::IntParameter udpSize("udpSize", "UDP packet data size", 1296, 500, 1400);
 
 extern settings_t settings;
 
@@ -95,10 +95,11 @@ void *udpserver(void *nport) {
 }
 
 // Send one packet, split into N UDP-sized pieces
-static uint8_t udpsend(WuClient *client, const uint8_t *data, unsigned len, uint32_t *id) {
+static uint8_t udpsend(WuClient *client, const uint8_t *data, unsigned len, uint32_t *id,
+			const uint32_t *frame) {
 	const uint32_t DATA_MAX = udpSize;
 
-	uint8_t buf[1400 + sizeof(uint32_t) * 4];
+	uint8_t buf[1400 + sizeof(uint32_t) * 5];
 	const uint32_t pieces = (len / DATA_MAX) + ((len % DATA_MAX) ? 1 : 0);
 
 	uint32_t i;
@@ -111,12 +112,13 @@ static uint8_t udpsend(WuClient *client, const uint8_t *data, unsigned len, uint
 		memcpy(&buf[4], &i, sizeof(uint32_t));
 		memcpy(&buf[8], &pieces, sizeof(uint32_t));
 		memcpy(&buf[12], &hash, sizeof(uint32_t));
+		memcpy(&buf[16], frame, sizeof(uint32_t));
 
-		memcpy(&buf[16], data, curlen);
+		memcpy(&buf[20], data, curlen);
 		data += curlen;
 		len -= curlen;
 
-		if (WuHostSendBinary(host, client, buf, curlen + sizeof(uint32_t) * 4) < 0)
+		if (WuHostSendBinary(host, client, buf, curlen + sizeof(uint32_t) * 5) < 0)
 			return 1;
 	}
 
@@ -125,7 +127,8 @@ static uint8_t udpsend(WuClient *client, const uint8_t *data, unsigned len, uint
 	return 0;
 }
 
-UdpStream::UdpStream(): OutStream(), client(NULL), total_len(0), id(0), failed(false) {
+UdpStream::UdpStream(): OutStream(), client(NULL), total_len(0), id(0), failed(false),
+	                frame(0) {
 	ptr = data;
 	end = data + UDPSTREAM_BUFSIZE;
 
@@ -137,7 +140,7 @@ void UdpStream::flush() {
 	total_len += len;
 
 	if (client) {
-		if (udpsend(client, data, len, &id)) {
+		if (udpsend(client, data, len, &id, &frame)) {
 			vlog.error("Error sending udp, client gone?");
 			failed = true;
 		}
diff --git a/common/network/Udp.h b/common/network/Udp.h
index 0bdeb22..38c9f46 100644
--- a/common/network/Udp.h
+++ b/common/network/Udp.h
@@ -40,6 +40,10 @@ namespace network {
 				client = cli;
 			}
 
+			void setFrameNumber(const unsigned in) {
+				frame = in;
+			}
+
 			bool isFailed() const;
 			void clearFailed();
 		private:
@@ -48,6 +52,7 @@ namespace network {
 			size_t total_len;
 			uint32_t id;
 			bool failed;
+			uint32_t frame;
 	};
 }
 
diff --git a/common/rfb/EncodeManager.cxx b/common/rfb/EncodeManager.cxx
index cc6f571..b6fa6af 100644
--- a/common/rfb/EncodeManager.cxx
+++ b/common/rfb/EncodeManager.cxx
@@ -363,6 +363,9 @@ void EncodeManager::doUpdate(bool allowLossy, const Region& changed_,
     unsigned screenArea;
 
     updates++;
+    if (conn->cp.supportsUdp)
+      ((network::UdpStream *) conn->getOutStream(conn->cp.supportsUdp))->setFrameNumber(updates);
+
 
     // The video resolution may have changed, check it
     if (conn->cp.kasmPassed[ConnParams::KASM_MAX_VIDEO_RESOLUTION])
diff --git a/common/rfb/SMsgWriter.cxx b/common/rfb/SMsgWriter.cxx
index aba2cdd..11c59c7 100644
--- a/common/rfb/SMsgWriter.cxx
+++ b/common/rfb/SMsgWriter.cxx
@@ -39,7 +39,7 @@ static LogWriter vlog("SMsgWriter");
 
 SMsgWriter::SMsgWriter(ConnParams* cp_, rdr::OutStream* os_, rdr::OutStream* udps_)
   : cp(cp_), os(os_), udps(udps_),
-    nRectsInUpdate(0), nRectsInHeader(0),
+    nRectsInUpdate(0), dataRectsInUpdate(0), nRectsInHeader(0),
     needSetDesktopSize(false), needExtendedDesktopSize(false),
     needSetDesktopName(false), needSetCursor(false),
     needSetXCursor(false), needSetCursorWithAlpha(false),
@@ -340,7 +340,7 @@ void SMsgWriter::writeFramebufferUpdateStart(int nRects)
 
   os->writeU16(nRects);
 
-  nRectsInUpdate = 0;
+  nRectsInUpdate = dataRectsInUpdate = 0;
   if (nRects == 0xFFFF)
     nRectsInHeader = 0;
   else
@@ -365,7 +365,7 @@ void SMsgWriter::writeFramebufferUpdateEnd()
 
     // Send an UDP flip marker, if needed
     if (cp->supportsUdp) {
-      udps->writeS16(0);
+      udps->writeS16(dataRectsInUpdate);
       udps->writeS16(0);
       udps->writeU16(0);
       udps->writeU16(0);
@@ -394,6 +394,7 @@ void SMsgWriter::startRect(const Rect& r, int encoding)
 {
   if (++nRectsInUpdate > nRectsInHeader && nRectsInHeader)
     throw Exception("SMsgWriter::startRect: nRects out of sync");
+  ++dataRectsInUpdate;
 
   if (cp->supportsUdp) {
     udps->writeS16(r.tl.x);
diff --git a/common/rfb/SMsgWriter.h b/common/rfb/SMsgWriter.h
index f16b03b..ba07c62 100644
--- a/common/rfb/SMsgWriter.h
+++ b/common/rfb/SMsgWriter.h
@@ -165,6 +165,7 @@ namespace rfb {
     rdr::OutStream* udps;
 
     int nRectsInUpdate;
+    int dataRectsInUpdate;
     int nRectsInHeader;
 
     bool needSetDesktopSize;