diff --git a/configure.ac b/configure.ac
index 367a072720..fb7c5c97d8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3687,7 +3687,7 @@ AS_IF([test "${universal_binary-no}" = yes ], [
 	for archs in ${universal_archnames}; do
 	    cpu=`echo $archs | sed 's/.*=//'`
 	    archs=`echo $archs | sed 's/=.*//'`
-	    RUBY_DEFINE_IF([defined __${archs}__], RUBY_PLATFORM_CPU, ["${cpu}"])
+	    RUBY_DEFINE_IF([defined __${archs}__ &&! defined RUBY_PLATFORM_CPU], RUBY_PLATFORM_CPU, ["${cpu}"])
 	done
     ])
     ints='long int short'
diff --git a/tool/m4/ruby_universal_arch.m4 b/tool/m4/ruby_universal_arch.m4
index 30f300a9fd..a524bc2592 100644
--- a/tool/m4/ruby_universal_arch.m4
+++ b/tool/m4/ruby_universal_arch.m4
@@ -14,10 +14,7 @@ AS_IF([test ${target_archs+set}], [
     for archs in $target_archs
     do
 	AS_CASE([",$universal_binary,"],[*",$archs,"*], [],[
-	    cpu=`$SHELL "$ac_aux_dir/config.sub" "${archs}-${target_os}" 2>&1` || {
-	        AC_MSG_RESULT([failed])
-		AC_MSG_ERROR([$cpu])
-	    }
+	    cpu=$archs
 	    cpu=`echo $cpu | sed 's/-.*-.*//'`
 	    universal_binary="${universal_binary+$universal_binary,}$cpu"
 	    universal_archnames="${universal_archnames} ${archs}=${cpu}"