diff --git a/libraries/AP_GPS/AP_GPS_Auto.cpp b/libraries/AP_GPS/AP_GPS_Auto.cpp
index 8be05dfdd3..b8be5d2eb5 100644
--- a/libraries/AP_GPS/AP_GPS_Auto.cpp
+++ b/libraries/AP_GPS/AP_GPS_Auto.cpp
@@ -79,7 +79,7 @@ AP_GPS_Auto::_detect(void)
 {
 	static uint32_t detect_started_ms;
 
-	if (detect_started_ms == 0) {
+	if (detect_started_ms == 0 && _port->available() > 0) {
 		detect_started_ms = millis();
 	}