diff --git a/mrbgems/mruby-rational/mrblib/rational.rb b/mrbgems/mruby-rational/mrblib/rational.rb
index ebe6829b0..688c660ab 100644
--- a/mrbgems/mruby-rational/mrblib/rational.rb
+++ b/mrbgems/mruby-rational/mrblib/rational.rb
@@ -6,6 +6,13 @@ class Rational < Numeric
   def to_s
     "#{numerator}/#{denominator}"
   end
+
+  def <=>(other)
+    return nil unless other.kind_of?(Numeric)
+    self.to_f <=> other.to_f
+  rescue
+    nil
+  end
 end
 
 class Numeric
diff --git a/mrbgems/mruby-rational/src/rational.c b/mrbgems/mruby-rational/src/rational.c
index f3ad57cd3..225a19636 100644
--- a/mrbgems/mruby-rational/src/rational.c
+++ b/mrbgems/mruby-rational/src/rational.c
@@ -387,62 +387,6 @@ rational_eq(mrb_state *mrb, mrb_value x)
   return mrb_bool_value(result);
 }
 
-static mrb_value
-rational_cmp(mrb_state *mrb, mrb_value x)
-{
-  struct mrb_rational *p1 = rational_ptr(mrb, x);
-  mrb_value y = mrb_get_arg1(mrb);
-
-  switch(mrb_type(y)) {
-  case MRB_TT_RATIONAL:
-    {
-      struct mrb_rational *p2 = rational_ptr(mrb, y);
-      mrb_int a, b;
-
-      if (mrb_int_mul_overflow(p1->numerator, p2->denominator, &a) ||
-          mrb_int_mul_overflow(p1->denominator, p2->numerator, &b)) {
-        return mrb_nil_value();
-      }
-      if (a > b)
-        return mrb_fixnum_value(1);
-      else if (a < b)
-        return mrb_fixnum_value(-1);
-      return mrb_fixnum_value(0);
-    }
-  case MRB_TT_INTEGER:
-#ifndef MRB_NO_FLOAT
-  case MRB_TT_FLOAT:
-    {
-      mrb_float a = rat_float(p1), b = mrb_as_float(mrb, y);
-      if (a > b)
-        return mrb_fixnum_value(1);
-      else if (a < b)
-        return mrb_fixnum_value(-1);
-      return mrb_fixnum_value(0);
-    }
-#else
-    {
-      mrb_int a = p1->numerator, b;
-      if (mrb_int_mul_overflow(p1->denominator, mrb_integer(y), &b)) {
-        return mrb_nil_value();
-      }
-      if (a > b)
-        return mrb_fixnum_value(1);
-      else if (a < b)
-        return mrb_fixnum_value(-1);
-      return mrb_fixnum_value(0);
-    }
-#endif
-  default:
-    x = mrb_funcall_argv(mrb, y, MRB_OPSYM(cmp), 1, &x);
-    if (mrb_integer_p(x)) {
-      mrb_int z = mrb_integer(x);
-      return mrb_fixnum_value(-z);
-    }
-    return mrb_nil_value();
- }
-}
-
 static mrb_value
 rational_minus(mrb_state *mrb, mrb_value x)
 {
@@ -733,7 +677,6 @@ void mrb_mruby_rational_gem_init(mrb_state *mrb)
   mrb_define_method_id(mrb, rat, MRB_SYM(to_r), mrb_obj_itself, MRB_ARGS_NONE());
   mrb_define_method_id(mrb, rat, MRB_SYM_Q(negative), rational_negative_p, MRB_ARGS_NONE());
   mrb_define_method_id(mrb, rat, MRB_OPSYM(eq), rational_eq, MRB_ARGS_REQ(1));
-  mrb_define_method_id(mrb, rat, MRB_OPSYM(cmp), rational_cmp, MRB_ARGS_REQ(1));
   mrb_define_method_id(mrb, rat, MRB_OPSYM(minus), rational_minus, MRB_ARGS_NONE());
   mrb_define_method_id(mrb, rat, MRB_OPSYM(add), rational_add, MRB_ARGS_REQ(1));
   mrb_define_method_id(mrb, rat, MRB_OPSYM(sub), rational_sub, MRB_ARGS_REQ(1));