diff --git a/.github/workflows/upstream.yml b/.github/workflows/upstream.yml
index 20bf392300..1c63c8078a 100644
--- a/.github/workflows/upstream.yml
+++ b/.github/workflows/upstream.yml
@@ -6,6 +6,12 @@ on:
   workflow_dispatch:
   schedule:
     - cron: "0 8 * * 1,3,5" # At 08:00 on Monday, Wednesday, and Friday # https://crontab.guru/#0_8_*_*_1,3,5
+  pull_request:
+    types: [opened, synchronize]
+    branches:
+      - '*'
+    paths:
+      - .github/workflows/upstream.yml # this file
 
 jobs:
   xmlsoft-head:
@@ -94,7 +100,7 @@ jobs:
       fail-fast: false
       matrix:
         sys: ["enable", "disable"]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04 # warning that 22.04 binary has dwarf5 debug info that valgrind can't read
     steps:
       - uses: actions/checkout@v3
         with:
diff --git a/test/xml/test_reader.rb b/test/xml/test_reader.rb
index 67f46c31c4..6d5060ae6c 100644
--- a/test/xml/test_reader.rb
+++ b/test/xml/test_reader.rb
@@ -684,7 +684,7 @@ def test_nonexistent_attribute
 
       def test_broken_markup_attribute_hash
         xml = <<~XML
-          <root><foo bar="asdf" xmlns:quux="qwer">
+          <root><foo bar="asdf" xmlns:quux="qwer">#{"x" * 1024}
         XML
         reader = Nokogiri::XML::Reader(xml)
         reader.read # root
@@ -696,15 +696,18 @@ def test_broken_markup_attribute_hash
         if Nokogiri.jruby?
           assert_equal({ "bar" => "asdf" }, reader.attribute_hash)
 
-          reader.read # text
+          reader.read # text (xxxxx)
+          reader.read # text (newline)
 
-          assert_raises(Nokogiri::XML::SyntaxError) do
+          e = assert_raises(Nokogiri::XML::SyntaxError) do
             reader.read
           end
+          assert_includes(e.message, "XML document structures must start and end")
         else
-          assert_raises(Nokogiri::XML::SyntaxError) do
+          e = assert_raises(Nokogiri::XML::SyntaxError) do
             reader.attribute_hash
           end
+          assert_includes(e.message, "FATAL: Extra content at the end of the document")
         end
 
         assert_equal(1, reader.errors.length)
@@ -712,7 +715,7 @@ def test_broken_markup_attribute_hash
 
       def test_broken_markup_namespaces
         xml = <<~XML
-          <root><foo bar="asdf" xmlns:quux="qwer">
+          <root><foo bar="asdf" xmlns:quux="qwer">#{"x" * 1024}
         XML
         reader = Nokogiri::XML::Reader(xml)
         reader.read # root
@@ -724,15 +727,18 @@ def test_broken_markup_namespaces
         if Nokogiri.jruby?
           assert_equal({ "xmlns:quux" => "qwer" }, reader.namespaces)
 
-          reader.read # text
+          reader.read # text (xxxxx)
+          reader.read # text (newline)
 
-          assert_raises(Nokogiri::XML::SyntaxError) do
+          e = assert_raises(Nokogiri::XML::SyntaxError) do
             reader.read
           end
+          assert_includes(e.message, "XML document structures must start and end")
         else
-          assert_raises(Nokogiri::XML::SyntaxError) do
+          e = assert_raises(Nokogiri::XML::SyntaxError) do
             reader.namespaces
           end
+          assert_includes(e.message, "FATAL: Extra content at the end of the document")
         end
 
         assert_equal(1, reader.errors.length)