diff --git a/src/ebusd/bushandler.cpp b/src/ebusd/bushandler.cpp
index 8bb95ea3..95fbd81f 100644
--- a/src/ebusd/bushandler.cpp
+++ b/src/ebusd/bushandler.cpp
@@ -603,8 +603,16 @@ result_t BusHandler::setState(BusState state, result_t result, bool firstRepetit
 		else if (state == bs_sendSyn || (result != RESULT_OK && !firstRepetition)) {
 			logDebug(lf_bus, "notify request: %s", getResultCode(result));
 			unsigned char dstAddress = m_currentRequest->m_master[1];
-			if (result == RESULT_OK && isValidAddress(dstAddress, false))
+			if (result == RESULT_OK && isValidAddress(dstAddress, false) && !m_seenAddresses[dstAddress]) {
+				if (m_autoLockCount) {
+					unsigned char master = getMasterAddress(dstAddress);
+					if (master != SYN && !m_seenAddresses[master]) {
+						m_seenAddresses[master] = true;
+						m_lockCount++;
+					}
+				}
 				m_seenAddresses[dstAddress] = true;
+			}
 			bool restart = m_currentRequest->notify(result, m_response);
 			if (restart) {
 				m_currentRequest->m_busLostRetries = 0;
@@ -664,15 +672,28 @@ void BusHandler::receiveCompleted()
 {
 	unsigned char srcAddress = m_command[0], dstAddress = m_command[1];
 	bool master = isMaster(dstAddress);
+	if (m_autoLockCount && isMaster(srcAddress) && !m_seenAddresses[srcAddress]) {
+		m_lockCount++;
+	}
 	m_seenAddresses[srcAddress] = true;
 	if (dstAddress == BROADCAST)
 		logInfo(lf_update, "update BC cmd: %s", m_command.getDataStr().c_str());
 	else if (master) {
 		logInfo(lf_update, "update MM cmd: %s", m_command.getDataStr().c_str());
+		if (m_autoLockCount && !m_seenAddresses[dstAddress]) {
+			m_lockCount++;
+		}
 		m_seenAddresses[dstAddress] = true;
 	}
 	else {
 		logInfo(lf_update, "update MS cmd: %s / %s", m_command.getDataStr().c_str(), m_response.getDataStr().c_str());
+		if (m_autoLockCount) {
+			unsigned char master = getMasterAddress(dstAddress);
+			if (master != SYN && !m_seenAddresses[master]) {
+				m_seenAddresses[master] = true;
+				m_lockCount++;
+			}
+		}
 		m_seenAddresses[dstAddress] = true;
 	}
 
@@ -736,8 +757,8 @@ result_t BusHandler::startScan(bool full)
 		if (!isValidAddress(slave, false) || isMaster(slave))
 			continue;
 		if (!full && !m_seenAddresses[slave]) {
-			unsigned char master = (unsigned char)(slave+256-5); // check if we saw the corresponding master already
-			if (!isMaster(master) || !m_seenAddresses[slave])
+			unsigned char master = getMasterAddress(slave); // check if we saw the corresponding master already
+			if (master == SYN || !m_seenAddresses[master])
 				continue;
 		}
 
diff --git a/src/ebusd/bushandler.h b/src/ebusd/bushandler.h
index 3e3aba37..de1d60d4 100644
--- a/src/ebusd/bushandler.h
+++ b/src/ebusd/bushandler.h
@@ -258,7 +258,7 @@ public:
 	 * @param failedSendRetries the number of times a failed send is repeated (other than lost arbitration).
 	 * @param slaveRecvTimeout the maximum time in microseconds an addressed slave is expected to acknowledge.
 	 * @param busAcquireTimeout the maximum time in microseconds for bus acquisition.
-	 * @param lockCount the number of AUTO-SYN symbols before sending is allowed after lost arbitration.
+	 * @param lockCount the number of AUTO-SYN symbols before sending is allowed after lost arbitration, or 0 for auto detection.
 	 * @param pollInterval the interval in seconds in which poll messages are cycled, or 0 if disabled.
 	 */
 	BusHandler(Device* device, MessageMap* messages,
@@ -270,7 +270,7 @@ public:
 		  m_ownMasterAddress(ownAddress), m_ownSlaveAddress((unsigned char)(ownAddress+5)), m_answer(answer),
 		  m_busLostRetries(busLostRetries), m_failedSendRetries(failedSendRetries),
 		  m_busAcquireTimeout(busAcquireTimeout), m_slaveRecvTimeout(slaveRecvTimeout),
-		  m_lockCount(lockCount), m_remainLockCount(lockCount),
+		  m_autoLockCount(lockCount==0), m_lockCount(lockCount==0 ? 1 : lockCount), m_remainLockCount(lockCount),
 		  m_pollInterval(pollInterval), m_lastReceive(0), m_lastPoll(0),
 		  m_currentRequest(NULL), m_nextSendPos(0),
 		  m_symPerSec(0), m_maxSymPerSec(0),
@@ -389,8 +389,11 @@ private:
 	/** the maximum time in microseconds an addressed slave is expected to acknowledge. */
 	const unsigned int m_slaveRecvTimeout;
 
+	/** whether m_lockCount shall be detected automatically. */
+	const bool m_autoLockCount;
+
 	/** the number of AUTO-SYN symbols before sending is allowed after lost arbitration. */
-	const unsigned int m_lockCount;
+	unsigned int m_lockCount;
 
 	/** the remaining number of AUTO-SYN symbols before sending is allowed again. */
 	unsigned int m_remainLockCount;