diff --git a/mrbgems/mruby-numeric-ext/mrblib/numeric_ext.rb b/mrbgems/mruby-numeric-ext/mrblib/numeric_ext.rb
index 576605cb1..8def77792 100644
--- a/mrbgems/mruby-numeric-ext/mrblib/numeric_ext.rb
+++ b/mrbgems/mruby-numeric-ext/mrblib/numeric_ext.rb
@@ -18,4 +18,34 @@ class Numeric
   def negative?
     self < 0
   end
+
+  ##
+  #  call-seq:
+  #    int.allbits?(mask)  ->  true or false
+  #
+  #  Returns +true+ if all bits of <code>+int+ & +mask+</code> are 1.
+  #
+  def allbits?(mask)
+    (self & mask) == mask
+  end
+
+  ##
+  #  call-seq:
+  #    int.anybits?(mask)  ->  true or false
+  #
+  #  Returns +true+ if any bits of <code>+int+ & +mask+</code> are 1.
+  #
+  def anybits?(mask)
+    (self & mask) != 0
+  end
+
+  ##
+  #  call-seq:
+  #    int.nobits?(mask)  ->  true or false
+  #
+  #  Returns +true+ if no bits of <code>+int+ & +mask+</code> are 1.
+  #
+  def nobits?(mask)
+    (self & mask) == 0
+  end
 end
diff --git a/mrbgems/mruby-numeric-ext/src/numeric_ext.c b/mrbgems/mruby-numeric-ext/src/numeric_ext.c
index 7ea0e9772..e2db07b9b 100644
--- a/mrbgems/mruby-numeric-ext/src/numeric_ext.c
+++ b/mrbgems/mruby-numeric-ext/src/numeric_ext.c
@@ -3,94 +3,6 @@
 #include <mruby/internal.h>
 #include <mruby/presym.h>
 
-#ifdef MRB_USE_BIGINT
-static mrb_value
-bint_allbits(mrb_state *mrb, mrb_value x, mrb_value y)
-{
-  y = mrb_as_bint(mrb, y);
-  x = mrb_bint_and(mrb, x, y);
-  if (mrb_bint_cmp(mrb, x, y) == 0) return mrb_true_value();
-  return mrb_false_value();
-}
-
-static mrb_value
-bint_anybits(mrb_state *mrb, mrb_value x, mrb_value y)
-{
-  y = mrb_as_bint(mrb, y);
-  x = mrb_bint_and(mrb, x, y);
-  if (mrb_bint_cmp(mrb, x, mrb_fixnum_value(0)) != 0)
-    return mrb_true_value();
-  return mrb_false_value();
-}
-
-static mrb_value
-bint_nobits(mrb_state *mrb, mrb_value x, mrb_value y)
-{
-  y = mrb_as_bint(mrb, y);
-  x = mrb_bint_and(mrb, x, y);
-  if (mrb_bint_cmp(mrb, x, mrb_fixnum_value(0)) == 0)
-    return mrb_true_value();
-  return mrb_false_value();
-}
-#endif
-
-/*
- *  call-seq:
- *     int.allbits?(mask)  ->  true or false
- *
- *  Returns +true+ if all bits of <code>+int+ & +mask+</code> are 1.
- */
-static mrb_value
-int_allbits(mrb_state *mrb, mrb_value self)
-{
-#ifdef MRB_USE_BIGINT
-  return bint_allbits(mrb, self, mrb_get_arg1(mrb));
-#endif
-  mrb_int n, m;
-
-  mrb_get_args(mrb, "i", &m);
-  n = mrb_integer(self);
-  return mrb_bool_value((n & m) == m);
-}
-
-/*
- *  call-seq:
- *     int.anybits?(mask)  ->  true or false
- *
- *  Returns +true+ if any bits of <code>+int+ & +mask+</code> are 1.
- */
-static mrb_value
-int_anybits(mrb_state *mrb, mrb_value self)
-{
-#ifdef MRB_USE_BIGINT
-  return bint_anybits(mrb, self, mrb_get_arg1(mrb));
-#endif
-  mrb_int n, m;
-
-  mrb_get_args(mrb, "i", &m);
-  n = mrb_integer(self);
-  return mrb_bool_value((n & m) != 0);
-}
-
-/*
- *  call-seq:
- *     int.nobits?(mask)  ->  true or false
- *
- *  Returns +true+ if no bits of <code>+int+ & +mask+</code> are 1.
- */
-static mrb_value
-int_nobits(mrb_state *mrb, mrb_value self)
-{
-#ifdef MRB_USE_BIGINT
-  return bint_nobits(mrb, self, mrb_get_arg1(mrb));
-#endif
-  mrb_int n, m;
-
-  mrb_get_args(mrb, "i", &m);
-  n = mrb_integer(self);
-  return mrb_bool_value((n & m) == 0);
-}
-
 #ifndef MRB_NO_FLOAT
 static mrb_value flo_remainder(mrb_state *mrb, mrb_value self);
 #endif
@@ -204,10 +116,6 @@ mrb_mruby_numeric_ext_gem_init(mrb_state* mrb)
 {
   struct RClass *i = mrb_class_get(mrb, "Integer");
 
-  mrb_define_method(mrb, i, "allbits?", int_allbits, MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, i, "anybits?", int_anybits, MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, i, "nobits?", int_nobits, MRB_ARGS_REQ(1));
-
   mrb_define_alias(mrb, i, "modulo", "%");
   mrb_define_method(mrb, i, "remainder", int_remainder, MRB_ARGS_REQ(1));