diff --git a/ChangeLog b/ChangeLog
index 9aa87e05cf..2ffc4cdb9a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Nov  7 15:22:37 2012  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* numeric.c (ruby_float_step): fix r37514: it yielded with NaN
+	  if the unit is infinity.
+
 Wed Nov  7 15:46:12 2012  Ayumu AIZAWA  <ayumu.aizawa@gmail.com>
 
 	* lib/webrick.rb: fix typo. reported by Rohit Arondekar.
diff --git a/numeric.c b/numeric.c
index bbe86a1708..aab049490d 100644
--- a/numeric.c
+++ b/numeric.c
@@ -1755,10 +1755,16 @@ ruby_float_step(VALUE from, VALUE to, VALUE step, int excl)
 	double n = ruby_float_step_size(beg, end, unit, excl);
 	long i;
 
-	for (i=0; i<n; i++) {
-	    double d = i*unit+beg;
-	    if (unit >= 0 ? end < d : d < end) d = end;
-	    rb_yield(DBL2NUM(d));
+	if (isinf(unit)) {
+	    /* if unit is infinity, i*unit+beg is NaN */
+	    if (n) rb_yield(DBL2NUM(beg));
+	}
+	else {
+	    for (i=0; i<n; i++) {
+		double d = i*unit+beg;
+		if (unit >= 0 ? end < d : d < end) d = end;
+		rb_yield(DBL2NUM(d));
+	    }
 	}
 	return TRUE;
     }
diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index 2ac394465f..288101f129 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -585,6 +585,10 @@ class TestFloat < Test::Unit::TestCase
     assert_equal([5.0, 4.0, 3.0, 2.0], 5.0.step(1.5, -1).to_a)
   end
 
+  def test_step2
+    assert_equal([0.0], 0.0.step(1.0, Float::INFINITY).to_a)
+  end
+
   def test_step_excl
     1000.times do
       a = rand