diff --git a/include/alt-voice.h b/include/alt-voice.h
index 49f799a..6d6a846 100644
--- a/include/alt-voice.h
+++ b/include/alt-voice.h
@@ -14,11 +14,11 @@ constexpr int FRAME_SIZE_BYTES = FRAME_SIZE_SAMPLES * sizeof(int16_t);
 AltVoiceError AV_Initialize();
 AltVoiceError AV_CreateSoundOutput(int bitrate, ISoundIO** soundOutput);
 AltVoiceError AV_CreateSoundInput(int bitrate, ISoundIO** soundInput);
-void AV_DestroySoundInput(ISoundIO* input);
+void AV_DestroySoundInput(const ISoundIO* input);
 const char* AV_GetVoiceErrorText(AltVoiceError error);
 AltVoiceError AV_CreateOpusEncoder(IOpusEncoder** opusEncoder, int bitRate);
 AltVoiceError AV_CreateOpusDecoder(IOpusDecoder** opusDecoder);
-void AV_DestroyOpusEncoder(IOpusEncoder* opusEncoder);
-void AV_DestroyOpusDecoder(IOpusDecoder* opusDecoder);
+void AV_DestroyOpusEncoder(const IOpusEncoder* opusEncoder);
+void AV_DestroyOpusDecoder(const IOpusDecoder* opusDecoder);
 AltVoiceError AV_CreateAudioFilter(IAudioFilter** audioFilter);
-void AV_DestroyAudioFilter(IAudioFilter* audioFilter);
+void AV_DestroyAudioFilter(const IAudioFilter* audioFilter);