diff --git a/simgear/sound/readwav.hxx b/simgear/sound/readwav.hxx
index 5e0a4b26..375b26ae 100644
--- a/simgear/sound/readwav.hxx
+++ b/simgear/sound/readwav.hxx
@@ -16,7 +16,7 @@ class SGPath;
 
 namespace simgear
 {
-  ALvoid* loadWAVFromFile(const SGPath& path, ALenum& format, ALsizei& size, ALfloat& freqf);
+  ALvoid* loadWAVFromFile(const SGPath& path, unsigned int& format, ALsizei& size, ALfloat& freqf);
   
   ALuint createBufferFromFile(const SGPath& path);
 }