diff --git a/stb_vorbis.c b/stb_vorbis.c
index b28944a..bc6fbe2 100644
--- a/stb_vorbis.c
+++ b/stb_vorbis.c
@@ -599,7 +599,9 @@ enum STBVorbisError
    #undef __forceinline
    #endif
    #define __forceinline
+   #ifndef alloca
    #define alloca __builtin_alloca
+   #endif
 #elif !defined(_MSC_VER)
    #if __GNUC__
       #define __forceinline inline