diff --git a/ChangeLog b/ChangeLog
index 3afb96c997..d54787449d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Thu Jun  6 09:41:00 2013  Kenta Murata  <mrkn@cookpad.com>
+
+	* numeric.c (num_quo): should return a Float for a Float argument.
+	  [ruby-dev:44710] [Bug #5515]
+
+	* test/ruby/test_fixnum.rb: Add an assertion for the above change.
+
+	* test/ruby/test_bignum.rb: ditto.
+
 Thu Jun  6 00:59:44 2013  Masaya Tarui  <tarui@ruby-lang.org>
 
 	* gc.c (gc_mark): get rid of pushing useless objests.
diff --git a/numeric.c b/numeric.c
index 89544dc745..e8d2f9df25 100644
--- a/numeric.c
+++ b/numeric.c
@@ -369,20 +369,6 @@ num_uminus(VALUE num)
     return rb_funcall(zero, '-', 1, num);
 }
 
-/*
- *  call-seq:
- *     num.quo(numeric)  ->  real
- *
- *  Returns most exact division (rational for integers, float for floats).
- */
-
-static VALUE
-num_quo(VALUE x, VALUE y)
-{
-    return rb_funcall(rb_rational_raw1(x), '/', 1, y);
-}
-
-
 /*
  *  call-seq:
  *     num.fdiv(numeric)  ->  float
@@ -397,6 +383,25 @@ num_fdiv(VALUE x, VALUE y)
 }
 
 
+/*
+ *  call-seq:
+ *     num.quo(int_or_rat)   ->  rat
+ *     num.quo(flo)          ->  flo
+ *
+ *  Returns most exact division (rational for integers, float for floats).
+ */
+
+static VALUE
+num_quo(VALUE x, VALUE y)
+{
+    if (RB_TYPE_P(y, T_FLOAT)) {
+        return num_fdiv(x, y);
+    }
+
+    return rb_funcall(rb_rational_raw1(x), '/', 1, y);
+}
+
+
 /*
  *  call-seq:
  *     num.div(numeric)  ->  integer
diff --git a/test/ruby/test_bignum.rb b/test/ruby/test_bignum.rb
index a3cba398e3..9f709daa8a 100644
--- a/test/ruby/test_bignum.rb
+++ b/test/ruby/test_bignum.rb
@@ -413,6 +413,8 @@ class TestBignum < Test::Unit::TestCase
   end
 
   def test_quo
+    assert_kind_of(Float, T32.quo(1.0))
+
     assert_equal(T32.to_f, T32.quo(1))
     assert_equal(T32.to_f, T32.quo(1.0))
     assert_equal(T32.to_f, T32.quo(T_ONE))
@@ -420,7 +422,7 @@ class TestBignum < Test::Unit::TestCase
     assert_raise(TypeError) { T32.quo("foo") }
 
     assert_equal(1024**1024, (1024**1024).quo(1))
-    assert_equal(1024**1024, (1024**1024).quo(1.0))
+    assert_equal(Float::INFINITY, (1024**1024).quo(1.0))
     assert_equal(1024**1024*2, (1024**1024*2).quo(1))
     inf = 1 / 0.0; nan = inf / inf
 
diff --git a/test/ruby/test_fixnum.rb b/test/ruby/test_fixnum.rb
index 85c8bdfa7b..c016b2f4e0 100644
--- a/test/ruby/test_fixnum.rb
+++ b/test/ruby/test_fixnum.rb
@@ -157,6 +157,7 @@ class TestFixnum < Test::Unit::TestCase
     assert_equal(0, 1 / (2**32))
     assert_equal(0, 1.div(2**32))
 
+    assert_kind_of(Float, 1.quo(2.0))
     assert_equal(0.5, 1.quo(2.0))
     assert_equal(0.5, 1 / 2.0)
     assert_equal(0, 1.div(2.0))