diff --git a/ChangeLog b/ChangeLog
index 6e5c83d95f..4f00cf278e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,7 @@
-Sat Mar 26 10:54:49 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Sat Mar 26 10:55:12 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* numeric.c (rb_int2str): conversion function to String for
+	  generic Integer.
 
 	* numeric.c (rb_int_round): rounding function for generic
 	  Integers.
diff --git a/internal.h b/internal.h
index e68e078e86..2f8c26f9e4 100644
--- a/internal.h
+++ b/internal.h
@@ -1014,6 +1014,7 @@ VALUE rb_int_mul(VALUE x, VALUE y);
 VALUE rb_int_idiv(VALUE x, VALUE y);
 VALUE rb_int_modulo(VALUE x, VALUE y);
 VALUE rb_int_round(VALUE num, int ndigits);
+VALUE rb_int2str(VALUE num, int base);
 VALUE rb_dbl_hash(double d);
 VALUE rb_fix_plus(VALUE x, VALUE y);
 
diff --git a/numeric.c b/numeric.c
index 7dc8b138a4..e368b59c3d 100644
--- a/numeric.c
+++ b/numeric.c
@@ -3022,7 +3022,12 @@ int_to_s(int argc, VALUE *argv, VALUE x)
 	rb_scan_args(argc, argv, "01", &b);
 	base = NUM2INT(b);
     }
+    return rb_int2str(x, base);
+}
 
+VALUE
+rb_int2str(VALUE x, int base)
+{
     if (FIXNUM_P(x)) {
 	return rb_fix2str(x, base);
     }