diff --git a/libraries/AP_Notify/MMLPlayer.cpp b/libraries/AP_Notify/MMLPlayer.cpp
index de179363d0..912799a680 100644
--- a/libraries/AP_Notify/MMLPlayer.cpp
+++ b/libraries/AP_Notify/MMLPlayer.cpp
@@ -106,7 +106,7 @@ size_t MMLPlayer::next_dots()
     return ret;
 }
 
-float MMLPlayer::rest_duration(uint32_t rest_length, uint8_t dots)
+float MMLPlayer::rest_duration(uint32_t rest_length, uint8_t dots) const
 {
     float whole_note_period = 240.0f / _tempo;
     if (rest_length == 0) {
diff --git a/libraries/AP_Notify/MMLPlayer.h b/libraries/AP_Notify/MMLPlayer.h
index 2f07b4980b..19372c6864 100644
--- a/libraries/AP_Notify/MMLPlayer.h
+++ b/libraries/AP_Notify/MMLPlayer.h
@@ -37,7 +37,7 @@ private:
     char next_char();
     uint8_t next_number();
     size_t next_dots();
-    float rest_duration(uint32_t rest_length, uint8_t dots);
+    float rest_duration(uint32_t rest_length, uint8_t dots) const;
 
     // Called when the MML player should start the next action
     void next_action();
diff --git a/libraries/AP_Notify/OreoLED_I2C.cpp b/libraries/AP_Notify/OreoLED_I2C.cpp
index f37ab52701..a9af37feee 100644
--- a/libraries/AP_Notify/OreoLED_I2C.cpp
+++ b/libraries/AP_Notify/OreoLED_I2C.cpp
@@ -701,7 +701,7 @@ void OreoLED_I2C::oreo_state::set_rgb(enum oreoled_pattern new_pattern, uint8_t
     phase_offset = new_phase_offset;
 }
 
-bool OreoLED_I2C::oreo_state::operator==(const OreoLED_I2C::oreo_state &os)
+bool OreoLED_I2C::oreo_state::operator==(const OreoLED_I2C::oreo_state &os) const
 {
     return ((os.mode==mode) && (os.pattern==pattern) && (os.macro==macro) && (os.red==red) && (os.green==green) && (os.blue==blue)
             && (os.amplitude_red==amplitude_red) && (os.amplitude_green==amplitude_green) && (os.amplitude_blue==amplitude_blue)
diff --git a/libraries/AP_Notify/OreoLED_I2C.h b/libraries/AP_Notify/OreoLED_I2C.h
index 29ea1c61e9..d1d4e1c652 100644
--- a/libraries/AP_Notify/OreoLED_I2C.h
+++ b/libraries/AP_Notify/OreoLED_I2C.h
@@ -164,7 +164,7 @@ private:
                      uint8_t new_blue, uint8_t new_amplitude_red, uint8_t new_amplitude_green, uint8_t new_amplitude_blue,
                      uint16_t new_period, uint16_t new_phase_offset);
 
-        bool operator==(const oreo_state &os);
+        bool operator==(const oreo_state &os) const;
     };
 
     typedef struct {