diff --git a/layout/base/crashtests/379799-1.html b/layout/base/crashtests/379799-1.html
new file mode 100644
index 00000000000..314744f7866
--- /dev/null
+++ b/layout/base/crashtests/379799-1.html
@@ -0,0 +1,31 @@
+<!DOCTYPE html>
+<html>
+<head>
+
+<style id="firstLetterSheet">
+  .fl:first-letter { }
+</style>
+
+<style id="emptySheet">
+</style>
+
+<script>
+
+function boom()
+{
+  document.getElementById("firstLetterSheet").textContent = "";
+  document.getElementById("emptySheet").textContent = ".aft:after { content: counter(chicken); }";
+}
+
+</script>
+
+</head>
+
+<body onload="boom()">
+
+<div class="fl">Foo <span class="aft">Bar</span></div>
+
+<p class="aft">Baz</p>
+
+</body>
+</html>
diff --git a/layout/base/crashtests/crashtests.list b/layout/base/crashtests/crashtests.list
index 5dd959f57fe..13fa9d0c171 100644
--- a/layout/base/crashtests/crashtests.list
+++ b/layout/base/crashtests/crashtests.list
@@ -16,5 +16,6 @@ load 364427-1.html
 load 366967-1.html
 load 372237-1.html
 load 372550-1.html
+load 379799-1.html
 load 379920-1.svg
 load 379920-2.svg
