diff --git a/src/serial.h b/src/serial.h
index 34e7560..7359415 100644
--- a/src/serial.h
+++ b/src/serial.h
@@ -92,7 +92,6 @@ int serial_read (serial_t *device, void* data, unsigned int size);
 int serial_write (serial_t *device, const void* data, unsigned int size);
 
 int serial_flush (serial_t *device, int queue);
-int serial_drain (serial_t *device);
 
 int serial_send_break (serial_t *device);
 
diff --git a/src/serial_posix.c b/src/serial_posix.c
index 2064c22..cdaa882 100644
--- a/src/serial_posix.c
+++ b/src/serial_posix.c
@@ -541,6 +541,14 @@ serial_write (serial_t *device, const void *data, unsigned int size)
 		nbytes += n;
 	}
 
+	// Wait until all data has been transmitted.
+	while (tcdrain (device->fd) != 0) {
+		if (errno != EINTR ) {
+			TRACE ("tcdrain");
+			return -1;
+		}
+	}
+
 	return nbytes;
 }
 
@@ -574,23 +582,6 @@ serial_flush (serial_t *device, int queue)
 }
 
 
-int
-serial_drain (serial_t *device)
-{
-	if (device == NULL)
-		return -1; // EINVAL (Invalid argument)
-
-	while (tcdrain (device->fd) != 0) {
-		if (errno != EINTR ) {
-			TRACE ("tcdrain");
-			return -1;
-		}
-	}
-
-	return 0;
-}
-
-
 int
 serial_send_break (serial_t *device)
 {
diff --git a/src/serial_win32.c b/src/serial_win32.c
index 8a9c619..299b130 100644
--- a/src/serial_win32.c
+++ b/src/serial_win32.c
@@ -399,21 +399,6 @@ serial_flush (serial_t *device, int queue)
 }
 
 
-int
-serial_drain (serial_t *device)
-{
-	if (device == NULL)
-		return -1; // ERROR_INVALID_PARAMETER (The parameter is incorrect)
-
-	if (!FlushFileBuffers (device->hFile)) {
-		TRACE ("FlushFileBuffers");
-		return -1;
-	}
-
-	return 0;
-}
-
-
 int
 serial_send_break (serial_t *device)
 {
diff --git a/src/suunto_d9.c b/src/suunto_d9.c
index b8cc021..8decadb 100644
--- a/src/suunto_d9.c
+++ b/src/suunto_d9.c
@@ -242,9 +242,6 @@ suunto_d9_device_packet (device_t *abstract, const unsigned char command[], unsi
 		return EXITCODE (n);
 	}
 
-	// Wait until all data has been transmitted.
-	serial_drain (device->port);
-
 	// Receive the echo.
 	unsigned char echo[128] = {0};
 	assert (sizeof (echo) >= csize);
diff --git a/src/suunto_vyper.c b/src/suunto_vyper.c
index 378ec7f..6cd9124 100644
--- a/src/suunto_vyper.c
+++ b/src/suunto_vyper.c
@@ -209,9 +209,6 @@ suunto_vyper_send (suunto_vyper_device_t *device, const unsigned char command[],
 		return EXITCODE (n);
 	}
 
-	// Wait until all data has been transmitted.
-	serial_drain (device->port);
-
 	// If the interface sends an echo back (which is the case for many clone 
 	// interfaces), this echo should be removed from the input queue before 
 	// attempting to read the real reply from the dive computer. Otherwise, 
diff --git a/src/suunto_vyper2.c b/src/suunto_vyper2.c
index 06cbd6b..32347dd 100644
--- a/src/suunto_vyper2.c
+++ b/src/suunto_vyper2.c
@@ -181,9 +181,6 @@ suunto_vyper2_device_packet (device_t *abstract, const unsigned char command[],
 		return EXITCODE (n);
 	}
 
-	// Wait until all data has been transmitted.
-	serial_drain (device->port);
-
 	serial_sleep (0x9);
 
 	// Clear RTS to receive the reply.