diff --git a/ChangeLog b/ChangeLog
index d8d93a2d1c..4d8d467610 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Mar 20 21:17:13 2016  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* internal.h (rb_int128t2big): declare only when HAVE_INT128_T.
+	  fixed a compile error with VC++ introduced at r54203.
+
 Sun Mar 20 20:10:14 2016  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* internal.h (DLONG): defined if long is 32bit (and LONG_LONG is 64bit;
diff --git a/internal.h b/internal.h
index f28d050b12..c30cc6ffed 100644
--- a/internal.h
+++ b/internal.h
@@ -272,9 +272,8 @@ nlz_int128(uint128_t x)
 #elif defined(HAVE_INT128_T)
 # define DLONG int128_t
 # define DL2NUM(x) (RB_FIXABLE(x) ? LONG2FIX(x) : rb_int128t2big(x))
-#endif
-
 VALUE rb_int128t2big(int128_t n);
+#endif
 
 /* arguments must be Fixnum */
 static inline VALUE