diff --git a/src/sound/oalsound.h b/src/sound/oalsound.h
index 4f6bae396..de9789f22 100644
--- a/src/sound/oalsound.h
+++ b/src/sound/oalsound.h
@@ -7,6 +7,8 @@
 
 #ifndef NO_OPENAL
 
+#define AL_NO_PROTOTYPES
+
 #include "al.h"
 #include "alc.h"