--- a/js/src/tests/ecma_5/Date/15.9.4.2.js
+++ b/js/src/tests/ecma_5/Date/15.9.4.2.js
@@ -124,10 +124,13 @@ function test()
   // different timezones
   check("2009-07-23T19:53:21.001+12:00", dd(2009,7,23,7,53,21,1));
   check("2009-07-23T00:53:21.001-07:00", dd(2009,7,23,7,53,21,1));
 
   // 00:00 and 24:00
   check("2009-07-23T00:00:00.000-07:00", dd(2009,7,23,7,0,0,0));
   check("2009-07-23T24:00:00.000-07:00", dd(2009,7,24,7,0,0,0));
 
+  // Bug 730838 - non-zero fraction part for midnight should produce NaN
+  checkInvalid("1970-01-01T24:00:00.500Z");
+
   exitFunc ('test');
 }