diff --git a/M17Control.cpp b/M17Control.cpp
index 3f98e5a..59ef2de 100644
--- a/M17Control.cpp
+++ b/M17Control.cpp
@@ -180,6 +180,15 @@ bool CM17Control::writeModem(unsigned char* data, unsigned int len)
 			std::string source = m_rfLICH.getSource();
 			std::string dest   = m_rfLICH.getDest();
 
+			if (m_selfOnly) {
+				bool ret = checkCallsign(source);
+				if (!ret) {
+					LogMessage("M17, invalid access attempt from %s to %s", source.c_str(), dest.c_str());
+					m_rfState = RS_RF_REJECTED;
+					return false;
+				}
+			}
+
 			unsigned char dataType = m_rfLICH.getDataType();
 			switch (dataType) {
 			case 1U:
@@ -269,6 +278,15 @@ bool CM17Control::writeModem(unsigned char* data, unsigned int len)
 				std::string source = m_rfLICH.getSource();
 				std::string dest   = m_rfLICH.getDest();
 
+				if (m_selfOnly) {
+					bool ret = checkCallsign(source);
+					if (!ret) {
+						LogMessage("M17, invalid access attempt from %s to %s", source.c_str(), dest.c_str());
+						m_rfState = RS_RF_REJECTED;
+						return false;
+					}
+				}
+
 				unsigned char dataType = m_rfLICH.getDataType();
 				switch (dataType) {
 				case 1U:
@@ -693,6 +711,13 @@ void CM17Control::decorrelator(const unsigned char* in, unsigned char* out) cons
 	}
 }
 
+bool CM17Control::checkCallsign(const std::string& callsign) const
+{
+	size_t len = m_callsign.size();
+
+	return m_callsign.compare(0U, len, callsign, 0U, len) == 0;
+}
+
 bool CM17Control::openFile()
 {
 	if (m_fp != NULL)
diff --git a/M17Control.h b/M17Control.h
index 1c2a271..71c402d 100644
--- a/M17Control.h
+++ b/M17Control.h
@@ -85,6 +85,8 @@ private:
 	void interleaver(const unsigned char* in, unsigned char* out) const;
 	void decorrelator(const unsigned char* in, unsigned char* out) const;
 
+	bool checkCallsign(const std::string& source) const;
+
 	unsigned int countBits(unsigned char byte);
 
 	void writeEndRF();
diff --git a/Version.h b/Version.h
index 0117c94..f1c220d 100644
--- a/Version.h
+++ b/Version.h
@@ -19,6 +19,6 @@
 #if !defined(VERSION_H)
 #define	VERSION_H
 
-const char* VERSION = "20201019";
+const char* VERSION = "20201020";
 
 #endif