diff --git a/css/css-contain/contain-layout-baseline-005.html b/css/css-contain/contain-layout-baseline-005.html
index 0971402e6b9f3a..fb706cbf0300eb 100644
--- a/css/css-contain/contain-layout-baseline-005.html
+++ b/css/css-contain/contain-layout-baseline-005.html
@@ -43,7 +43,6 @@
 <div class="wrapper">
   <canvas></canvas>
   <div class="inline-block">foo</div>
-  <button>foo</button>
   <select><option>foo</option></select>
   <select multiple style="height: 40px;"><option>foo</option></select>
   <textarea style="height: 40px;"></textarea>
diff --git a/css/css-contain/contain-layout-button-001.html b/css/css-contain/contain-layout-button-001.tentative.html
similarity index 92%
rename from css/css-contain/contain-layout-button-001.html
rename to css/css-contain/contain-layout-button-001.tentative.html
index b53b28879e2ce8..f5a664e566f6bc 100644
--- a/css/css-contain/contain-layout-button-001.html
+++ b/css/css-contain/contain-layout-button-001.tentative.html
@@ -5,7 +5,7 @@
 <link rel="help" href="https://drafts.csswg.org/css-contain-1/#containment-layout">
 <link rel="help" href="https://drafts.csswg.org/css2/visudet.html#propdef-vertical-align">
 <link rel="match" href="reference/contain-layout-button-001-ref.html">
-<meta name=assert content="Layout containment does apply to buttons, thus their baseline is their margin-bottom edge.">
+<meta name=assert content="Layout containment does apply to buttons, but in an inline context their baseline is synthesized from their content-box.">
 <style>
 button {
   border: 5px solid green;
diff --git a/css/css-contain/contain-layout-button-002.tentative.html b/css/css-contain/contain-layout-button-002.tentative.html
new file mode 100644
index 00000000000000..15026d55f8c637
--- /dev/null
+++ b/css/css-contain/contain-layout-button-002.tentative.html
@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<link rel="help" href="https://drafts.csswg.org/css-contain-1/#containment-layout">
+<link rel="help" href="https://github.com/web-platform-tests/wpt/issues/45889">
+<link rel="match" href="reference/contain-layout-button-002-ref.html">
+<meta name=assert content="An empty button and a button with layout containment should align the same.">
+<style>
+button {
+  border: 5px solid green;
+  padding: 10px;
+  margin-bottom: 2px;
+  color: transparent;
+  width: 20px;
+  height: 20px;
+}
+</style>
+
+<p>This test passes if it has the same output as the reference.</p>
+<button></button> <button style="contain:layout"></button>
diff --git a/css/css-contain/reference/contain-layout-baseline-005-ref.html b/css/css-contain/reference/contain-layout-baseline-005-ref.html
index 360652c9397ee8..83340137ac6ac9 100644
--- a/css/css-contain/reference/contain-layout-baseline-005-ref.html
+++ b/css/css-contain/reference/contain-layout-baseline-005-ref.html
@@ -39,7 +39,6 @@
 <div class="wrapper">
   <canvas></canvas>
   <div class="inline-block">foo</div>
-  <button>foo</button>
   <select><option>foo</option></select>
   <select multiple style="height: 40px;"><option>foo</option></select>
   <textarea style="height: 40px;"></textarea>
diff --git a/css/css-contain/reference/contain-layout-button-001-ref.html b/css/css-contain/reference/contain-layout-button-001-ref.html
index da83204dce641b..c20efbbb39d4cc 100644
--- a/css/css-contain/reference/contain-layout-button-001-ref.html
+++ b/css/css-contain/reference/contain-layout-button-001-ref.html
@@ -7,7 +7,7 @@
   display: inline-block;
   border: 5px solid green;
   padding: 0;
-  margin-bottom: 2px;
+  margin-bottom: -5px;
   color: transparent;
   width: 0;
   height: 0px;
diff --git a/css/css-contain/reference/contain-layout-button-002-ref.html b/css/css-contain/reference/contain-layout-button-002-ref.html
new file mode 100644
index 00000000000000..85b98ee4a66b1a
--- /dev/null
+++ b/css/css-contain/reference/contain-layout-button-002-ref.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<style>
+button {
+  border: 5px solid green;
+  padding: 10px;
+  margin-bottom: 2px;
+  color: transparent;
+  width: 20px;
+  height: 20px;
+}
+</style>
+<p>This test passes if it has the same output as the reference.</p>
+<button></button> <button></button>
