diff --git a/code/nel/include/nel/sound/driver/sound_driver.h b/code/nel/include/nel/sound/driver/sound_driver.h
index 193026a42..2fa450249 100644
--- a/code/nel/include/nel/sound/driver/sound_driver.h
+++ b/code/nel/include/nel/sound/driver/sound_driver.h
@@ -41,7 +41,7 @@ namespace NLSOUND
 /*
  * Sound sample format
  */
-enum TSampleFormat { SampleFormatUnknown, Mono8, Mono16ADPCM, Mono16, Stereo8, Stereo16 };
+enum TSampleFormat { Mono8, Mono16ADPCM, Mono16, Stereo8, Stereo16, SampleFormatUnknown = (~0) };
 
 /**
  * Abstract sound driver (implemented in sound driver dynamic library)