diff --git a/ChangeLog b/ChangeLog
index 7c71a98d47..8a8a571141 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Nov 28 05:10:23 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (--with-setup): add option to select ext/Setup file.
+
 Fri Nov 28 05:02:29 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* dmyenc.c (Init_enc): separate from dmyext.c for statically
diff --git a/configure.in b/configure.in
index 7b29193e59..d0f22706aa 100644
--- a/configure.in
+++ b/configure.in
@@ -3247,7 +3247,14 @@ AS_CASE([",$EXTSTATIC,"], [,static,|*,enc,*], [
 AC_SUBST(ENCOBJS)
 AC_SUBST(EXTOBJS)
 
-if test -f "$srcdir/ext/Setup.$target_os"; then
+AC_ARG_WITH(setup,
+	    AS_HELP_STRING([--with-setup=SETUP], [use extension libraries setup]),
+	    [setup=$withval])
+if test -n "$setup"; then
+    if ! test -f "ext/$setup" -o -f "$srcdir/ext/$setup"; then
+	AC_MSG_ERROR(Setup file $setup not found under ext or $srcdir/ext)
+    fi
+elif test -f "$srcdir/ext/Setup.$target_os"; then
     setup="Setup.$target_os"
 else
     setup=