diff --git a/content/html/content/src/nsHTMLObjectElement.cpp b/content/html/content/src/nsHTMLObjectElement.cpp
index 5043bdf1467d..33ded82c01fb 100644
--- a/content/html/content/src/nsHTMLObjectElement.cpp
+++ b/content/html/content/src/nsHTMLObjectElement.cpp
@@ -360,7 +360,7 @@ NS_IMPL_STRING_ATTR(nsHTMLObjectElement, Height, height)
 NS_IMPL_INT_ATTR(nsHTMLObjectElement, Hspace, hspace)
 NS_IMPL_STRING_ATTR(nsHTMLObjectElement, Name, name)
 NS_IMPL_STRING_ATTR(nsHTMLObjectElement, Standby, standby)
-NS_IMPL_INT_ATTR(nsHTMLObjectElement, TabIndex, tabindex)
+NS_IMPL_INT_ATTR_DEFAULT_VALUE(nsHTMLObjectElement, TabIndex, tabindex, 0)
 NS_IMPL_STRING_ATTR(nsHTMLObjectElement, Type, type)
 NS_IMPL_STRING_ATTR(nsHTMLObjectElement, UseMap, usemap)
 NS_IMPL_INT_ATTR(nsHTMLObjectElement, Vspace, vspace)
diff --git a/content/html/content/test/Makefile.in b/content/html/content/test/Makefile.in
index fc5621fa25fa..e950c286362f 100644
--- a/content/html/content/test/Makefile.in
+++ b/content/html/content/test/Makefile.in
@@ -158,6 +158,7 @@ _TEST_FILES = 	test_bug589.html \
 		test_bug536891.html \
 		test_bug536895.html \
 		test_bug458037.xhtml \
+		test_bug556645.html \
 		test_bug559284.html \
         test_bug551670.html \
         test_bug346485.html \
diff --git a/content/html/content/test/test_bug556645.html b/content/html/content/test/test_bug556645.html
new file mode 100644
index 000000000000..8fc40a9ad5fa
--- /dev/null
+++ b/content/html/content/test/test_bug556645.html
@@ -0,0 +1,50 @@
+<html>
+<head>
+  <title>Test for Bug 556645</title>
+  <script type="text/javascript" src="/MochiKit/packed.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body onload="runTest()">
+<script>
+SimpleTest.waitForExplicitFinish();
+
+function runTest()
+{
+  var obj = document.getElementById("obj");
+  var childDoc = obj.contentDocument;
+  var body = childDoc.body;
+  is(document.activeElement, document.body, "focus in parent before");
+  is(childDoc.activeElement, body, "focus in child before");
+
+  var button = childDoc.getElementsByTagName("button")[0];
+  button.focus();
+  childDoc.defaultView.focus();
+  is(document.activeElement, obj, "focus in parent after focus()");
+  is(childDoc.activeElement, button, "focus in child after focus()");
+
+  button.blur();
+  var pbutton = document.getElementById("pbutton");
+  pbutton.focus();
+
+  synthesizeKey("VK_TAB", { });
+  is(document.activeElement, obj, "focus in parent after tab");
+  is(childDoc.activeElement, childDoc.documentElement, "focus in child after tab");
+
+  synthesizeKey("VK_TAB", { });
+  is(document.activeElement, obj, "focus in parent after tab 2");
+  is(childDoc.activeElement, button, "focus in child after tab 2");
+
+  SimpleTest.finish();
+}
+
+</script>
+
+<button id="pbutton">Parent</button>
+<object id="obj" type="text/html"
+        data="data:text/html,%3Cbody%3E%3Cbutton%3EChild%3C/button%3E%3C/body%3E"
+        width="200" height="200"></object>
+
+</body>
+</html>
