diff --git a/ChangeLog b/ChangeLog
index dc85786c9c..c1eab5d950 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,12 @@ Tue Sep  3 07:31:29 2013  Akinori MUSHA  <knu@iDaemons.org>
 	* numeric.c (NUM_STEP_SCAN_ARGS): Numeral#step should raise
 	  TypeError if a non-numeric parameter is given.
 
+	* test/ruby/test_float.rb (TestFloat#test_num2dbl): Allow nil as
+	  step, as with the keyword argument.
+
+	* test/ruby/test_numeric.rb (TestNumeric#test_step): Add tests for
+	  nil as step or limit.
+
 Tue Sep  3 07:28:49 2013  Tanaka Akira  <akr@fsij.org>
 
 	* internal.h (bit_length): Add casts to fix complation error with
diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index f011c2b062..c55b051832 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -561,9 +561,6 @@ class TestFloat < Test::Unit::TestCase
     assert_raise(TypeError) do
       1.0.step(2.0, "0.5") {}
     end
-    assert_raise(TypeError) do
-      1.0.step(2.0, nil) {}
-    end
   end
 
   def test_sleep_with_Float
diff --git a/test/ruby/test_numeric.rb b/test/ruby/test_numeric.rb
index a4bd5960f4..d2f211245d 100644
--- a/test/ruby/test_numeric.rb
+++ b/test/ruby/test_numeric.rb
@@ -227,11 +227,20 @@ class TestNumeric < Test::Unit::TestCase
     assert_raise(ArgumentError) { 1.step(10, 1, 0).size }
     assert_raise(ArgumentError) { 1.step(10, 0) { } }
     assert_raise(ArgumentError) { 1.step(10, 0).size }
+    assert_raise(TypeError) { 1.step(10, "1") { } }
+    assert_raise(TypeError) { 1.step(10, "1").size }
+    assert_nothing_raised { 1.step(10, nil) { } }
+    assert_nothing_raised { 1.step(10, nil).size }
+    assert_nothing_raised { 1.step(by: 0, to: nil) }
+    assert_nothing_raised { 1.step(by: 0, to: nil).size }
     assert_nothing_raised { 1.step(by: 0) }
     assert_nothing_raised { 1.step(by: 0).size }
+    assert_nothing_raised { 1.step(by: nil) }
+    assert_nothing_raised { 1.step(by: nil).size }
 
     assert_step [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [1, 10]
     assert_step [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [1, to: 10]
+    assert_step [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [1, to: 10, by: nil]
     assert_step [1, 3, 5, 7, 9], [1, 10, 2]
     assert_step [1, 3, 5, 7, 9], [1, to: 10, by: 2]
 
@@ -251,6 +260,7 @@ class TestNumeric < Test::Unit::TestCase
 
     assert_step [10, 11, 12, 13], [10], inf: true
     assert_step [10, 9, 8, 7], [10, by: -1], inf: true
+    assert_step [10, 9, 8, 7], [10, by: -1, to: nil], inf: true
   end
 
   def test_num2long