diff --git a/serial_darwin.go b/serial_darwin.go
index ad970a8..a9c8109 100644
--- a/serial_darwin.go
+++ b/serial_darwin.go
@@ -46,6 +46,11 @@ var databitsMap = map[int]int{
 const tcCMSPAR int = 0 // may be CMSPAR or PAREXT
 const tcIUCLC int = 0
 
+const tcCCTS_OFLOW int = 0x00010000
+const tcCRTS_IFLOW int = 0x00020000
+
+const tcCRTSCTS int = (tcCCTS_OFLOW | tcCRTS_IFLOW)
+
 // syscall wrappers
 
 //sys ioctl(fd int, req uint64, data uintptr) (err error)
diff --git a/serial_freebsd.go b/serial_freebsd.go
index 318e25c..55b02f8 100644
--- a/serial_freebsd.go
+++ b/serial_freebsd.go
@@ -48,6 +48,11 @@ var databitsMap = map[int]int{
 const tcCMSPAR int = 0 // may be CMSPAR or PAREXT
 const tcIUCLC int = 0
 
+const tcCCTS_OFLOW int = 0x00010000
+const tcCRTS_IFLOW int = 0x00020000
+
+const tcCRTSCTS int = tcCCTS_OFLOW
+
 func termiosMask(data int) uint32 {
 	return uint32(data)
 }
diff --git a/serial_linux.go b/serial_linux.go
index 983975f..9308ace 100644
--- a/serial_linux.go
+++ b/serial_linux.go
@@ -58,6 +58,8 @@ var databitsMap = map[int]int{
 const tcCMSPAR int = 0 // may be CMSPAR or PAREXT
 const tcIUCLC = syscall.IUCLC
 
+const tcCRTSCTS int = 0x80000000
+
 func termiosMask(data int) uint32 {
 	return uint32(data)
 }
diff --git a/serial_unix.go b/serial_unix.go
index d03c4bd..c71dc53 100644
--- a/serial_unix.go
+++ b/serial_unix.go
@@ -203,6 +203,9 @@ func setRawMode(settings *syscall.Termios) {
 	// Set local mode
 	settings.Cflag |= termiosMask(syscall.CREAD | syscall.CLOCAL)
 
+	// Explicitly disable RTS/CTS flow control
+	settings.Cflag &= ^termiosMask(tcCRTSCTS)
+
 	// Set raw mode
 	settings.Lflag &= ^termiosMask(syscall.ICANON | syscall.ECHO | syscall.ECHOE | syscall.ECHOK |
 		syscall.ECHONL | syscall.ECHOCTL | syscall.ECHOPRT | syscall.ECHOKE | syscall.ISIG | syscall.IEXTEN)