diff --git a/inc/MicroBitRadio.h b/inc/MicroBitRadio.h
index 9244b7f9..fae47f62 100644
--- a/inc/MicroBitRadio.h
+++ b/inc/MicroBitRadio.h
@@ -205,7 +205,7 @@ namespace codal
          * A background, low priority callback that is triggered whenever the processor is idle.
          * Here, we empty our queue of received packets, and pass them onto higher level protocol handlers.
          */
-        virtual void idleCallback();
+        virtual void idleCallback() override;
 
         /**
          * Determines the number of packets ready to be processed.
diff --git a/inc/MicroBitThermometer.h b/inc/MicroBitThermometer.h
index 99573d94..810e9618 100644
--- a/inc/MicroBitThermometer.h
+++ b/inc/MicroBitThermometer.h
@@ -123,7 +123,7 @@ namespace codal
         /**
          * Periodic callback from MicroBit idle thread.
          */
-        virtual void idleCallback();
+        virtual void idleCallback() override;
 
         private:
 
diff --git a/inc/Mixer2.h b/inc/Mixer2.h
index c07f01a1..6ef27b7e 100644
--- a/inc/Mixer2.h
+++ b/inc/Mixer2.h
@@ -78,7 +78,7 @@ class MixerChannel : public DataSink
     /**
      * Deliver the next available ManagedBuffer to our downstream caller.
      */
-    virtual int pullRequest();
+    virtual int pullRequest() override;
     virtual ~MixerChannel() {};
 
     /**
@@ -169,14 +169,14 @@ class Mixer2 : public DataSource
     /**
      * Provide the next available ManagedBuffer to our downstream caller, if available.
      */
-    virtual ManagedBuffer pull();
+    virtual ManagedBuffer pull() override;
 
     /**
      * Define a downstream component for data stream.
      *
      * @sink The component that data will be delivered to, when it is availiable
      */
-    virtual void connect(DataSink &sink);
+    virtual void connect(DataSink &sink) override;
 
     /**
      * Determines if this source is connected to a downstream component
@@ -184,12 +184,12 @@ class Mixer2 : public DataSource
      * @return true If a downstream is connected
      * @return false If a downstream is not connected
      */
-    bool isConnected();
+    virtual bool isConnected() override;
 
     /**
      * Determines the output format for the Mixer.
      */
-    virtual int getFormat();
+    virtual int getFormat() override;
 
     /**
      * Defines the output format for the Mixer.
@@ -199,7 +199,7 @@ class Mixer2 : public DataSource
      * DATASTREAM_FORMAT_8BIT_UNSIGNED
      * DATASTREAM_FORMAT_8BIT_SIGNED
      */
-    virtual int setFormat(int format);
+    virtual int setFormat(int format) override;
 
 
     /**
@@ -241,7 +241,7 @@ class Mixer2 : public DataSource
      * Determine the sample rate output of this Mixer.
      * @return The sample rate (samples per second) of the mixer output.
      */
-    float getSampleRate();
+    virtual float getSampleRate() override;
 
     /**
      * Defines an optional bit mask to logical OR with each sample.
diff --git a/inc/NRF52LedMatrix.h b/inc/NRF52LedMatrix.h
index a6491bea..cae296ec 100644
--- a/inc/NRF52LedMatrix.h
+++ b/inc/NRF52LedMatrix.h
@@ -122,7 +122,7 @@ namespace codal
          *
          * @note Only enables the display if the display is currently disabled.
          */
-        virtual void enable();
+        virtual void enable() override;
 
         /**
          * Disables the display, which releases control of the GPIO pins used by the display,
@@ -134,7 +134,7 @@ namespace codal
          *
          * @note Only disables the display if the display is currently enabled.
          */
-        virtual void disable();
+        virtual void disable() override;
 
         /**
          * Clears the display of any remaining pixels.
@@ -154,7 +154,7 @@ namespace codal
          *
          * @return DEVICE_OK, or DEVICE_INVALID_PARAMETER
          */
-        int setBrightness(int b);
+        virtual int setBrightness(int b) override;
 
         /**
          * Determines the last ambient light level sensed.
diff --git a/inc/SoundEmojiSynthesizer.h b/inc/SoundEmojiSynthesizer.h
index 9c218ca9..176eff2f 100644
--- a/inc/SoundEmojiSynthesizer.h
+++ b/inc/SoundEmojiSynthesizer.h
@@ -166,7 +166,7 @@ namespace codal
          * @return true If a downstream is connected
          * @return false If a downstream is not connected
          */
-        bool isConnected();
+        virtual bool isConnected() override;
 
         /**
          *  Determine the data format of the buffers streamed out of this component.
@@ -207,7 +207,7 @@ namespace codal
          * Determine the sample rate currently in use by this Synthesizer.
          * @return the current sample rate, in Hz.
          */
-        float getSampleRate();
+        virtual float getSampleRate() override;
 
         /**
          * Change the sample rate used by this Synthesizer,
diff --git a/inc/SoundOutputPin.h b/inc/SoundOutputPin.h
index a8b18aa0..ddbc40e4 100644
--- a/inc/SoundOutputPin.h
+++ b/inc/SoundOutputPin.h
@@ -163,8 +163,8 @@ namespace codal
         /**
           * Relevant DataSource operations
           */
-        virtual ManagedBuffer pull();
-        virtual int getFormat();
+        virtual ManagedBuffer pull() override;
+        virtual int getFormat() override;
         
         /**
          * Determines if this source is connected to a downstream component
@@ -172,7 +172,7 @@ namespace codal
          * @return true If a downstream is connected
          * @return false If a downstream is not connected
          */
-        bool isConnected();
+        virtual bool isConnected() override;
 
         private:
 
diff --git a/inc/bluetooth/MicroBitBLEManager.h b/inc/bluetooth/MicroBitBLEManager.h
index af655d74..f9d93d95 100644
--- a/inc/bluetooth/MicroBitBLEManager.h
+++ b/inc/bluetooth/MicroBitBLEManager.h
@@ -184,7 +184,7 @@ class MicroBitBLEManager : public CodalComponent
      * Periodic callback in thread context.
      * We use this here purely to safely issue a disconnect operation after a pairing operation is complete.
 	 */
-    void idleCallback();
+    virtual void idleCallback() override;
 
     /**
 	* Stops any currently running BLE advertisements
diff --git a/inc/bluetooth/MicroBitEventService.h b/inc/bluetooth/MicroBitEventService.h
index 6920c83c..1917c581 100644
--- a/inc/bluetooth/MicroBitEventService.h
+++ b/inc/bluetooth/MicroBitEventService.h
@@ -63,7 +63,7 @@ class MicroBitEventService : public MicroBitBLEService, MicroBitComponent
      * Periodic callback from MicroBit scheduler.
      * If we're no longer connected, remove any registered Message Bus listeners.
      */
-    virtual void idleCallback();
+    virtual void idleCallback() override;
 
     /**
       * Callback. Invoked when any of our attributes are written via BLE.
diff --git a/inc/bluetooth/MicroBitIOPinService.h b/inc/bluetooth/MicroBitIOPinService.h
index 2ba80176..a58aaec7 100644
--- a/inc/bluetooth/MicroBitIOPinService.h
+++ b/inc/bluetooth/MicroBitIOPinService.h
@@ -80,7 +80,7 @@ class MicroBitIOPinService : public MicroBitBLEService, MicroBitComponent
      * Check if any of the pins we're watching need updating. Notify any connected
      * device with any changes.
      */
-    virtual void idleCallback();
+    virtual void idleCallback() override;
 
     private: