diff --git a/ChangeLog b/ChangeLog
index f0faaa1bb0..661710a2ed 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Jun 28 01:08:42 2008  Tanaka Akira  <akr@fsij.org>
+
+	* time.c (time_timespec): fix rounding negative float.
+
 Fri Jun 27 21:38:57 2008  Tanaka Akira  <akr@fsij.org>
 
 	* struct.c: __size__ removed.  use the length of __members__ instead.
diff --git a/test/ruby/test_time.rb b/test/ruby/test_time.rb
index 9cbb6eaca6..c0620323fc 100644
--- a/test/ruby/test_time.rb
+++ b/test/ruby/test_time.rb
@@ -105,6 +105,18 @@ class TestTime < Test::Unit::TestCase
     assert_equal(100, Time.at(0.0000001).nsec)
     assert_equal(10, Time.at(0.00000001).nsec)
     assert_equal(1, Time.at(0.000000001).nsec)
+    assert_equal(0, Time.at(1e-10).nsec)
+    assert_equal(0, Time.at(4e-10).nsec)
+    assert_equal(1, Time.at(6e-10).nsec)
+    assert_equal(1, Time.at(14e-10).nsec)
+    assert_equal(2, Time.at(16e-10).nsec)
+    if negative_time_t?
+      assert_equal(0, Time.at(-1e-10).nsec)
+      assert_equal(0, Time.at(-4e-10).nsec)
+      assert_equal(999999999, Time.at(-6e-10).nsec)
+      assert_equal(999999999, Time.at(-14e-10).nsec)
+      assert_equal(999999998, Time.at(-16e-10).nsec)
+    end
   end
 
   def test_at2
diff --git a/time.c b/time.c
index c35c9a15f4..08f4eb8282 100644
--- a/time.c
+++ b/time.c
@@ -201,6 +201,10 @@ time_timespec(VALUE num, int interval)
 	    double f, d;
 
 	    d = modf(RFLOAT_VALUE(num), &f);
+            if (d < 0) {
+                d += 1;
+                f -= 1;
+            }
 	    t.tv_sec = (time_t)f;
 	    if (f != t.tv_sec) {
 		rb_raise(rb_eRangeError, "%f out of Time range", RFLOAT_VALUE(num));