--- libmpeg2-0.5.1/configure.ac~	2009-07-09 10:07:51.000000000 +0200
+++ libmpeg2-0.5.1/configure.ac	2009-07-09 10:08:42.000000000 +0200
@@ -76,13 +76,15 @@
 	for TRY_CFLAGS in "-mpim-altivec -force_cpusubtype_ALL" -faltivec -maltivec -fvec; do
 	    AC_TRY_CFLAGS([$OPT_CFLAGS $TRY_CFLAGS $CFLAGS],
 		[save_CFLAGS="$CFLAGS"
-		 CFLAGS="$OPT_CFLAGS $TRY_CFLAGS $CFLAGS"
+		 CFLAGS="$OPT_CFLAGS $TRY_CFLAGS $CFLAGS -Werror"
 		 AC_MSG_CHECKING([if <altivec.h> is needed])
 		 AC_TRY_COMPILE([],
 		    [typedef vector int t;
 		     vec_ld(0, (unsigned char *)0);],
 		    [have_altivec=yes; AC_MSG_RESULT(no)],
-		    [AC_TRY_COMPILE([#include <altivec.h>],
+		    [CFLAGS="$save_CFLAGS"
+		     CFLAGS="$OPT_CFLAGS $TRY_CFLAGS $CFLAGS"
+		     AC_TRY_COMPILE([#include <altivec.h>],
 			[typedef vector int t; vec_ld(0, (unsigned char *)0);],
 			[AC_DEFINE([HAVE_ALTIVEC_H],,
 			    [Define to 1 if you have the <altivec.h> header.])