diff --git a/ChangeLog b/ChangeLog
index 46afa32836..d8bc414359 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,6 @@
-Mon Oct  7 21:03:54 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Mon Oct  7 22:45:20 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
-	* configure.in, win32/Makefile.sub (FIBER_USE_NATIVE): move conditions
-	  from cont.c
+	* cont.c (FIBER_USE_NATIVE): split long conditions.
 
 Mon Oct  7 20:29:31 2013  Zachary Scott  <e@zzak.io>
 
diff --git a/configure.in b/configure.in
index 04bdbb926c..c23f691325 100644
--- a/configure.in
+++ b/configure.in
@@ -2352,23 +2352,11 @@ if test x"$enable_pthread" = xyes; then
       AC_CHECK_FUNCS(pthread_attr_init)
     fi
 fi
-FIBER_USE_NATIVE=0
 if test x"$ac_cv_header_ucontext_h" = xyes; then
     if test x"$rb_with_pthread" = xyes; then
 	AC_CHECK_FUNCS(getcontext setcontext)
-	if test x"$ac_cv_func_getcontext" = xyes -a x"$ac_cv_func_setcontext" = xyes; then
-	    AS_CASE("$target_cpu-$target_os",
-		[*-netbsd*], [],
-		[ia64-*], [], # r38766
-		[*-sunos*|*-solaris*], [], # r32408
-		[FIBER_USE_NATIVE=1])
-	fi
     fi
-else
-    AS_CASE("$target_os", [mingw*|mswin*],
-	    [test "[$[with_winnt_ver]]" -ge [$[0x0400]] && FIBER_USE_NATIVE=1])
 fi
-AC_DEFINE(FIBER_USE_NATIVE)
 
 if test "$ac_cv_func_fork" = "yes" -a "$rb_with_pthread" = "yes"; then
     AC_CACHE_CHECK([if fork works with pthread], rb_cv_fork_with_pthread,
diff --git a/cont.c b/cont.c
index 75fa3d5418..d09b21bb31 100644
--- a/cont.c
+++ b/cont.c
@@ -15,6 +15,20 @@
 #include "gc.h"
 #include "eval_intern.h"
 
+#if !defined(FIBER_USE_NATIVE)
+# if defined(HAVE_GETCONTEXT) && defined(HAVE_SETCONTEXT)
+#   if defined(__NetBSD__)
+#   elif defined(__sun)
+#   elif defined(__ia64)
+#   else
+#     define FIBER_USE_NATIVE 1
+#   endif
+# elif defined(_WIN32)
+#   if _WIN32_WINNT >= 0x0400
+#     define FIBER_USE_NATIVE 1
+#   endif
+# endif
+
 /* FIBER_USE_NATIVE enables Fiber performance improvement using system
  * dependent method such as make/setcontext on POSIX system or
  * CreateFiber() API on Windows.
@@ -31,6 +45,7 @@
  * are represented by stack pointer (higher bits of stack pointer).
  * TODO: check such constraint on configure.
  */
+#endif
 #if !defined(FIBER_USE_NATIVE)
 #define FIBER_USE_NATIVE 0
 #endif
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index 519dc8cd51..d10e82986c 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -692,9 +692,6 @@ $(CONFIG_H): $(MKFILES) $(srcdir)/win32/Makefile.sub $(win_srcdir)/Makefile.sub
 !if "$(MACHINE)" == "x86" || "$(ARCH)" == "x64" || "$(ARCH)" == "ia64"
 #define STACK_GROW_DIRECTION -1
 !endif
-!if "$(ARCH)" != "ia64" && NTVER >= 0x0400 # r27646
-#define FIBER_USE_NATIVE 1
-!endif
 #define CANONICALIZATION_FOR_MATHN 1
 #define DEFAULT_KCODE KCODE_NONE
 !if "$(ENABLE_DEBUG_ENV)" == "yes"