diff --git a/serial_win32.c b/serial_win32.c
index 3439f47..2a224d5 100644
--- a/serial_win32.c
+++ b/serial_win32.c
@@ -105,6 +105,14 @@ serial_open (serial** out, const char* name)
 		return -1;
 	}
 
+	// Set the event mask for the drain function.
+	if (!SetCommMask (device->hFile, EV_TXEMPTY)) {
+		TRACE ("SetCommMask");
+		CloseHandle (device->hFile);
+		free (device);
+		return -1;
+	}
+
 	*out = device;
 
 	return 0;
@@ -376,6 +384,17 @@ serial_drain (serial* device)
 	if (device == NULL)
 		return -1; // ERROR_INVALID_PARAMETER (The parameter is incorrect)
 
+	BOOL rc = 0;
+	DWORD mask = 0;
+	do {
+		rc = WaitCommEvent (device->hFile, &mask, NULL);
+	} while ( rc && !(mask & EV_TXEMPTY) );
+
+	if (!rc) {
+		TRACE ("WaitCommEvent");
+		return -1;
+	}
+
 	return 0;
 }