diff --git a/libraries/RC_Channel/RC_Channel.cpp b/libraries/RC_Channel/RC_Channel.cpp
index 3de5f72684ed5829e2c081c7a70d7f73d070143f..4c801285ed77f6993fdf9854917d8bb5199e0c68 100644
--- a/libraries/RC_Channel/RC_Channel.cpp
+++ b/libraries/RC_Channel/RC_Channel.cpp
@@ -230,7 +230,7 @@ RC_Channel::calc_pwm(void)
   used for thr_mid in copter
  */
 int16_t
-RC_Channel::get_control_mid() {
+RC_Channel::get_control_mid() const {
     if (_type == RC_CHANNEL_TYPE_RANGE) {
         int16_t r_in = (radio_min.get()+radio_max.get())/2;
 
diff --git a/libraries/RC_Channel/RC_Channel.h b/libraries/RC_Channel/RC_Channel.h
index 16a34c104d3df0d51f8f52bdaf116a167285e450..1224603a1e70dbd0e092810c44c42219c42aa967 100644
--- a/libraries/RC_Channel/RC_Channel.h
+++ b/libraries/RC_Channel/RC_Channel.h
@@ -62,7 +62,7 @@ public:
     uint8_t     get_ch_out(void) const { return _ch_out; };
 
     // get the center stick position expressed as a control_in value
-    int16_t     get_control_mid();
+    int16_t     get_control_mid() const;
 
     // read input from APM_RC - create a control_in value
     void        set_pwm(int16_t pwm);