diff --git a/layout/base/nsPresContext.h b/layout/base/nsPresContext.h
index d0fd07c15bc3..7ee9fdc3a58e 100644
--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -427,7 +427,7 @@ public:
 
   /**
    * Get the visible area associated with this presentation context.
-   * This is the size of the visiable area that is used for
+   * This is the size of the visible area that is used for
    * presenting the document. The returned value is in the standard
    * nscoord units (as scaled by the device context).
    */
diff --git a/layout/base/tests/Makefile.in b/layout/base/tests/Makefile.in
index 76efd20a286c..b8d2ed7c199e 100644
--- a/layout/base/tests/Makefile.in
+++ b/layout/base/tests/Makefile.in
@@ -94,6 +94,7 @@ _TEST_FILES =	\
 		test_bug445810.html \
 		test_bug449781.html \
 		test_bug450930.xhtml \
+		test_bug458898.html \
 		$(NULL)
 # test_bug396024.html is currently disabled because it interacts badly with
 # the "You can't print-preview while the page is loading" dialog.
diff --git a/layout/base/tests/test_bug458898.html b/layout/base/tests/test_bug458898.html
new file mode 100644
index 000000000000..b2f15c805e23
--- /dev/null
+++ b/layout/base/tests/test_bug458898.html
@@ -0,0 +1,38 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=458898
+-->
+<head>
+  <title>Test for Bug 458898</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+  <script type="application/javascript" src="/tests/SimpleTest/EventUtils.js"></script>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=458898">Mozilla Bug 458898</a>
+<p id="display"></p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+SimpleTest.waitForExplicitFinish();
+netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
+var win = window.openDialog("data:text/html,<div style='height:200px; width:100px;'>");
+
+function loaded() {
+  win.sizeToContent();
+  ok(win.innerWidth >= 100, "innerWidth");
+  ok(win.innerHeight >= 200, "innerHeight");
+  win.close();
+  SimpleTest.finish();
+}
+
+win.addEventListener("load", loaded, false);
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/layout/generic/nsHTMLFrame.cpp b/layout/generic/nsHTMLFrame.cpp
index e3045eb2fec8..40cf6d15e5ff 100644
--- a/layout/generic/nsHTMLFrame.cpp
+++ b/layout/generic/nsHTMLFrame.cpp
@@ -709,9 +709,16 @@ CanvasFrame::Reflow(nsPresContext*           aPresContext,
       viewport->Invalidate(nsRect(nsPoint(0, 0), viewport->GetSize()));
     }
     
-    // Return our desired size (which doesn't matter)
+    // Return our desired size. Normally it's what we're told, but
+    // sometimes we can be given an unconstrained height (when a window
+    // is sizing-to-content), and we should compute our desired height.
     aDesiredSize.width = aReflowState.ComputedWidth();
-    aDesiredSize.height = aReflowState.ComputedHeight();
+    if (aReflowState.ComputedHeight() == NS_UNCONSTRAINEDSIZE) {
+      aDesiredSize.height = kidFrame->GetRect().height +
+        kidReflowState.mComputedMargin.TopBottom();
+    } else {
+      aDesiredSize.height = aReflowState.ComputedHeight();
+    }
 
     aDesiredSize.mOverflowArea.UnionRect(
       nsRect(0, 0, aDesiredSize.width, aDesiredSize.height),
