diff --git a/Lib/test/test_datetime.py b/Lib/test/test_datetime.py
index 2528b4a..203bea1 100644
--- a/Lib/test/test_datetime.py
+++ b/Lib/test/test_datetime.py
@@ -1400,6 +1400,12 @@
         got = self.theclass.utcfromtimestamp(ts)
         self.verify_field_equality(expected, got)
 
+    def test_microsecond_rounding(self):
+        # Test whether fromtimestamp "rounds up" floats that are less
+        # than one microsecond smaller than an integer.
+        self.assertEquals(self.theclass.fromtimestamp(0.9999999),
+                          self.theclass.fromtimestamp(1))
+
     def test_insane_fromtimestamp(self):
         # It's possible that some platform maps time_t to double,
         # and that this test will fail there.  This test should
diff --git a/Modules/datetimemodule.c b/Modules/datetimemodule.c
index b7bddff..648ebe5 100644
--- a/Modules/datetimemodule.c
+++ b/Modules/datetimemodule.c
@@ -3683,6 +3683,13 @@
 		return NULL;
 	fraction = timestamp - (double)timet;
 	us = (int)round_to_long(fraction * 1e6);
+	/* If timestamp is less than one microsecond smaller than a
+	 * full second, round up. Otherwise, ValueErrors are raised
+	 * for some floats. */
+	if (us == 1000000) {
+		timet += 1;
+		us = 0;
+	}
 	return datetime_from_timet_and_us(cls, f, timet, us, tzinfo);
 }