diff --git a/Modem.cpp b/Modem.cpp
index 850b2e6..df2c9c5 100644
--- a/Modem.cpp
+++ b/Modem.cpp
@@ -301,7 +301,7 @@ bool CModem::open()
 		return false;
 	}
 
-	if (m_fmEnabled) {
+	if (m_fmEnabled && m_duplex) {
 		ret = setFMCallsignParams();
 		if (!ret) {
 			m_serial->close();
@@ -1528,7 +1528,7 @@ bool CModem::setConfig()
 		buffer[4U] |= 0x10U;
 	if (m_pocsagEnabled)
 		buffer[4U] |= 0x20U;
-	if (m_fmEnabled)
+	if (m_fmEnabled && m_duplex)
 		buffer[4U] |= 0x40U;
 
 	buffer[5U] = m_txDelay / 10U;		// In 10ms units
diff --git a/Version.h b/Version.h
index 049e6ea..4029d27 100644
--- a/Version.h
+++ b/Version.h
@@ -19,6 +19,6 @@
 #if !defined(VERSION_H)
 #define	VERSION_H
 
-const char* VERSION = "20200418";
+const char* VERSION = "20200419";
 
 #endif