diff --git a/src/audio/alsa/SDL_alsa_audio.c b/src/audio/alsa/SDL_alsa_audio.c
index 180064f31..13cc77bf6 100644
--- a/src/audio/alsa/SDL_alsa_audio.c
+++ b/src/audio/alsa/SDL_alsa_audio.c
@@ -643,7 +643,7 @@ ALSA_OpenDevice(_THIS, const char *devname, int iscapture)
         ALSA_CloseDevice(this);
         return SDL_OutOfMemory();
     }
-    SDL_memset(this->hidden->mixbuf, this->spec.silence, this->spec.size);
+    SDL_memset(this->hidden->mixbuf, this->spec.silence, this->hidden->mixlen);
 
     /* Switch to blocking mode for playback */
     ALSA_snd_pcm_nonblock(pcm_handle, 0);
diff --git a/src/audio/alsa/SDL_alsa_audio.h b/src/audio/alsa/SDL_alsa_audio.h
index 5a4bf7fcf..31c653403 100644
--- a/src/audio/alsa/SDL_alsa_audio.h
+++ b/src/audio/alsa/SDL_alsa_audio.h
@@ -20,8 +20,8 @@
 */
 #include "SDL_config.h"
 
-#ifndef _ALSA_PCM_audio_h
-#define _ALSA_PCM_audio_h
+#ifndef _SDL_ALSA_audio_h
+#define _SDL_ALSA_audio_h
 
 #include <alsa/asoundlib.h>
 
@@ -40,6 +40,6 @@ struct SDL_PrivateAudioData
     int mixlen;
 };
 
-#endif /* _ALSA_PCM_audio_h */
+#endif /* _SDL_ALSA_audio_h */
 
 /* vi: set ts=4 sw=4 expandtab: */