diff --git a/ChangeLog b/ChangeLog
index c6f79c2073..f8e4a70224 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat May 21 21:07:18 2016  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* configure.in (ALWAYS_INLINE): force compilers the function inlined.
+
 Sat May 21 16:16:03 2016  Kazuki Yamaguchi  <k@rhe.jp>
 
 	* ext/openssl/ossl_ssl.c (ossl_ssl_stop): Don't free the SSL struct
diff --git a/configure.in b/configure.in
index 52d97a6af8..9c4cd1812a 100644
--- a/configure.in
+++ b/configure.in
@@ -1807,6 +1807,7 @@ RUBY_FUNC_ATTRIBUTE(__deprecated__, DEPRECATED)
 RUBY_FUNC_ATTRIBUTE(__deprecated__("by "@%:@n), DEPRECATED_BY(n,x), rb_cv_func_deprecated_by)
 RUBY_TYPE_ATTRIBUTE(__deprecated__ mesg, DEPRECATED_TYPE(mesg,x), rb_cv_type_deprecated)
 RUBY_FUNC_ATTRIBUTE(__noinline__, NOINLINE)
+RUBY_FUNC_ATTRIBUTE(__always_inline__, ALWAYS_INLINE)
 RUBY_FUNC_ATTRIBUTE(__error__, ERRORFUNC)
 RUBY_FUNC_ATTRIBUTE(__warning__, WARNINGFUNC)
 RUBY_FUNC_ATTRIBUTE(__weak__, WEAK, rb_cv_func_weak)
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index 8a235d7ce2..d2f89eea5f 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -596,6 +596,7 @@ $(CONFIG_H): $(MKFILES) $(srcdir)/win32/Makefile.sub $(win_srcdir)/Makefile.sub
 #define DEPRECATED_TYPE(mesg, x) __declspec(deprecated mesg) x
 #define NOINLINE(x) __declspec(noinline) x
 !endif
+#define ALWAYS_INLINE(x) __forceinline x
 #define UNREACHABLE __assume(0)
 #define ASSUME(x) __assume(!!(x))
 #define FUNC_STDCALL(x) __stdcall x