diff --git a/include/media/AudioSystem.h b/include/media/AudioSystem.h
index 26a0bb2..d4b25f0 100644
--- a/include/media/AudioSystem.h
+++ b/include/media/AudioSystem.h
@@ -312,7 +312,7 @@
 
     static audio_mode_t getPhoneState();
 
-    static status_t registerPolicyMixes(Vector<AudioMix> mixes, bool registration);
+    static status_t registerPolicyMixes(const Vector<AudioMix>& mixes, bool registration);
 
     static status_t startAudioSource(const struct audio_port_config *source,
                                       const audio_attributes_t *attributes,
diff --git a/include/media/IAudioPolicyService.h b/include/media/IAudioPolicyService.h
index 6b93f6f..5919fe5 100644
--- a/include/media/IAudioPolicyService.h
+++ b/include/media/IAudioPolicyService.h
@@ -159,7 +159,7 @@
 
     virtual audio_mode_t getPhoneState() = 0;
 
-    virtual status_t registerPolicyMixes(Vector<AudioMix> mixes, bool registration) = 0;
+    virtual status_t registerPolicyMixes(const Vector<AudioMix>& mixes, bool registration) = 0;
 
     virtual status_t startAudioSource(const struct audio_port_config *source,
                                       const audio_attributes_t *attributes,
diff --git a/include/media/RingBuffer.h b/include/media/RingBuffer.h
index df7c00e..4d92d87 100644
--- a/include/media/RingBuffer.h
+++ b/include/media/RingBuffer.h
@@ -39,7 +39,7 @@
     /**
      * Construct a RingBuffer that can grow up to the given length.
      */
-    RingBuffer(size_t length);
+    explicit RingBuffer(size_t length);
 
     /**
      * Forward iterator to this class.  Implements an std:forward_iterator.