diff --git a/desmume/configure.ac b/desmume/configure.ac
index 873cf6eec..cbdac8305 100644
--- a/desmume/configure.ac
+++ b/desmume/configure.ac
@@ -260,6 +260,7 @@ case $host in
     AC_DEFINE(HAVE_OPENAL)
     LIBS="$LIBS -framework OpenGL -framework OpenAL"
     CPPFLAGS="$CPPFLAGS -I/System/Library/Frameworks/OpenAL.framework/Headers"
+	AC_SUBST(CPPFLAGS)
     dnl - extra hackery needed for X includes
     AC_PATH_XTRA
     ;;