diff --git a/YSF2DMR/Conf.cpp b/YSF2DMR/Conf.cpp
index 7c4d4ef..8ed8ad8 100644
--- a/YSF2DMR/Conf.cpp
+++ b/YSF2DMR/Conf.cpp
@@ -240,6 +240,8 @@ bool CConf::read()
 			m_dmrIdLookupFile = value;
 		else if (::strcmp(key, "Time") == 0)
 			m_dmrIdLookupTime = (unsigned int)::atoi(value);
+		if (::strcmp(key, "DropUnknown") == 0)
+			m_dmrDropUnknown = ::atoi(value) == 1;
 	} else if (section == SECTION_LOG) {
 		if (::strcmp(key, "FilePath") == 0)
 			m_logFilePath = value;
@@ -517,6 +519,11 @@ unsigned int CConf::getDMRIdLookupTime() const
 	return m_dmrIdLookupTime;
 }
 
+bool CConf::getDMRDropUnknown() const
+{
+	return m_dmrDropUnknown;
+}
+
 unsigned int CConf::getLogDisplayLevel() const
 {
 	return m_logDisplayLevel;
diff --git a/YSF2DMR/Conf.h b/YSF2DMR/Conf.h
index 92e8228..4f1faa7 100644
--- a/YSF2DMR/Conf.h
+++ b/YSF2DMR/Conf.h
@@ -79,6 +79,7 @@ public:
   // The DMR Id section
   std::string  getDMRIdLookupFile() const;
   unsigned int getDMRIdLookupTime() const;
+  bool         getDMRDropUnknown() const;
 
   // The Log section
   unsigned int getLogDisplayLevel() const;
@@ -141,6 +142,7 @@ private:
 
   std::string  m_dmrIdLookupFile;
   unsigned int m_dmrIdLookupTime;
+  bool         m_dmrDropUnknown;
 
   unsigned int m_logDisplayLevel;
   unsigned int m_logFileLevel;
diff --git a/YSF2DMR/YSF2DMR.cpp b/YSF2DMR/YSF2DMR.cpp
index 7aadb47..6da18b1 100644
--- a/YSF2DMR/YSF2DMR.cpp
+++ b/YSF2DMR/YSF2DMR.cpp
@@ -292,6 +292,7 @@ int CYSF2DMR::run()
 
 	m_lookup = new CDMRLookup(lookupFile, reloadTime);
 	m_lookup->read();
+	m_dropUnknown = m_conf.getDMRDropUnknown();
 
 	if (m_dmrpc)
 		m_dmrflco = FLCO_USER_USER;
@@ -581,21 +582,33 @@ int CYSF2DMR::run()
 							m_dmrNetwork->reset(2U);	// OE1KBC fix
 							
 							m_srcid = findYSFID(ysfSrc, true);
-							m_conv.putYSFHeader();
-							m_ysfFrames = 0U;
+							if (m_dropUnknown == 0 || m_srcid != 0) {
+								ysfWatchdog.start();
+								m_dmrNetwork->reset(2U);	// OE1KBC fix
+								 m_conv.putYSFHeader();
+								m_ysfFrames = 0U;
+							}
+							else
+							{
+								LogMessage("Dropped source without DMR ID: %s", ysfSrc.c_str());
+							}
 						}
 					} else if (fi == YSF_FI_TERMINATOR) {
-						ysfWatchdog.stop();
-						int extraFrames = (m_hangTime / 100U) - m_ysfFrames - 2U;
-						for (int i = 0U; i < extraFrames; i++)
-							m_conv.putDummyYSF();
-						LogMessage("YSF received end of voice transmission, %.1f seconds", float(m_ysfFrames) / 10.0F);
-						m_conv.putYSFEOT();
-						m_ysfFrames = 0U;
+						if (m_dropUnknown == 0 || m_srcid != 0) {
+							ysfWatchdog.stop();
+							int extraFrames = (m_hangTime / 100U) - m_ysfFrames - 2U;
+							for (int i = 0U; i < extraFrames; i++)
+								m_conv.putDummyYSF();
+							LogMessage("YSF received end of voice transmission, %.1f seconds", float(m_ysfFrames) / 10.0F);
+							m_conv.putYSFEOT();
+							m_ysfFrames = 0U;
+						}
 					} else if (fi == YSF_FI_COMMUNICATIONS) {
-						ysfWatchdog.start();
-						m_conv.putYSF(buffer + 35U);
-						m_ysfFrames++;
+						if (m_dropUnknown == 0 || m_srcid != 0) {
+							ysfWatchdog.start();
+							m_conv.putYSF(buffer + 35U);
+							m_ysfFrames++;
+						}
 					}
 				}
 
@@ -1255,7 +1268,7 @@ unsigned int CYSF2DMR::findYSFID(std::string cs, bool showdst)
 		dmrpc = false;
 
 	if (id == 0) {
-		id = m_defsrcid;
+		if (m_dropUnknown == 0) id = m_defsrcid;
 		if (showdst)
 			LogMessage("Not DMR ID found, using default ID: %u, DstID: %s%u", id, dmrpc ? "" : "TG ", m_dstid);
 		else
diff --git a/YSF2DMR/YSF2DMR.h b/YSF2DMR/YSF2DMR.h
index a645e9e..957f796 100644
--- a/YSF2DMR/YSF2DMR.h
+++ b/YSF2DMR/YSF2DMR.h
@@ -107,6 +107,7 @@ private:
 	bool             m_remoteGateway;
 	unsigned int     m_hangTime;
 	bool             m_firstSync;
+	bool             m_dropUnknown;
 
 	bool createDMRNetwork();
 	void createGPS();
diff --git a/YSF2DMR/YSF2DMR.ini b/YSF2DMR/YSF2DMR.ini
index 9855351..60c25a3 100644
--- a/YSF2DMR/YSF2DMR.ini
+++ b/YSF2DMR/YSF2DMR.ini
@@ -46,6 +46,7 @@ Debug=0
 [DMR Id Lookup]
 File=DMRIds.dat
 Time=24
+DropUnknown=0
 
 [Log]
 # Logging levels, 0=No logging