diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 0b9eb75b8f4..1bfcf112c45 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -1318,6 +1318,7 @@ impl LayoutThread {
&mut layout_context);
}
+ self.first_reflow.set(false);
self.respond_to_query_if_necessary(&data.reflow_goal,
&mut *rw_data,
&mut layout_context,
@@ -1618,8 +1619,6 @@ impl LayoutThread {
&mut *layout_context,
rw_data);
- self.first_reflow.set(false);
-
if opts::get().trace_layout {
layout_debug::end_trace(self.generation.get());
}
diff --git a/tests/wpt/mozilla/meta/MANIFEST.json b/tests/wpt/mozilla/meta/MANIFEST.json
index 75e8b9a0a4a..8ea28218101 100644
--- a/tests/wpt/mozilla/meta/MANIFEST.json
+++ b/tests/wpt/mozilla/meta/MANIFEST.json
@@ -14546,6 +14546,12 @@
{}
]
],
+ "mozilla/first-reflow-sheet-assert.html": [
+ [
+ "/_mozilla/mozilla/first-reflow-sheet-assert.html",
+ {}
+ ]
+ ],
"mozilla/focus_blur.html": [
[
"/_mozilla/mozilla/focus_blur.html",
@@ -27925,6 +27931,10 @@
"f2ec5f89521fb4eda64a5e70249bbfb8850c4278",
"testharness"
],
+ "mozilla/first-reflow-sheet-assert.html": [
+ "8a0cf9152c3f2421d3e418f824f02c915092d78f",
+ "testharness"
+ ],
"mozilla/focus_blur.html": [
"2735c5c482e38743b0976789af858075c54408c1",
"testharness"
diff --git a/tests/wpt/mozilla/tests/mozilla/first-reflow-sheet-assert.html b/tests/wpt/mozilla/tests/mozilla/first-reflow-sheet-assert.html
new file mode 100644
index 00000000000..268af6d333f
--- /dev/null
+++ b/tests/wpt/mozilla/tests/mozilla/first-reflow-sheet-assert.html
@@ -0,0 +1,16 @@
+
+
+Issue 18631: Assertion failure when double-adding the UA sheets to the page
+
+
+
+