diff --git a/APMrover2/mode.cpp b/APMrover2/mode.cpp
index 0bdade9f2d..2c4549e90f 100644
--- a/APMrover2/mode.cpp
+++ b/APMrover2/mode.cpp
@@ -216,6 +216,16 @@ void Mode::set_desired_speed_to_default(bool rtl)
     _desired_speed = get_speed_default(rtl);
 }
 
+// set desired speed in m/s
+bool Mode::set_desired_speed(float speed)
+{
+    if (!is_negative(speed)) {
+        _desired_speed = speed;
+        return true;
+    }
+    return false;
+}
+
 void Mode::calc_throttle(float target_speed, bool nudge_allowed, bool avoidance_enabled)
 {
     // add in speed nudging
diff --git a/APMrover2/mode.h b/APMrover2/mode.h
index 5183dc9821..78e5a4bde7 100644
--- a/APMrover2/mode.h
+++ b/APMrover2/mode.h
@@ -104,8 +104,8 @@ public:
     // rtl argument should be true if called from RTL or SmartRTL modes (handled here to avoid duplication)
     float get_speed_default(bool rtl = false) const;
 
-    // set desired speed
-    void set_desired_speed(float speed) { _desired_speed = speed; }
+    // set desired speed in m/s
+    bool set_desired_speed(float speed);
 
     // restore desired speed to default from parameter values (CRUISE_SPEED or WP_SPEED)
     // rtl argument should be true if called from RTL or SmartRTL modes (handled here to avoid duplication)