diff --git a/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003-ref.html b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003-ref.html
index 176526e55b2586..b3e3e8d2f1ad6e 100644
--- a/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003-ref.html
+++ b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003-ref.html
@@ -10,5 +10,5 @@
 </style>
 
 <div class="div-parent">
-  <div>Testline1<br><br><br>Testline2<br><br><br>Testline3</div>
+  <div><br>Testline1<br><br><br>Testline2<br><br><br>Testline3<br><br></div>
 </div>
diff --git a/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003.html b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003.html
index dc5e3204c98e9e..e33c0d0b40dd31 100644
--- a/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003.html
+++ b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-003.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
-<title>text-box-trim trims through invisible line boxes</title>
+<title>text-box-trim should only be applied on the first/last formatted line</title>
 <link rel="help" href="https://drafts.csswg.org/css-inline-3/#text-box-trim">
-<link rel="help" href="https://www.w3.org/TR/css-inline-3/#invisible-line-boxes">
+<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#first-formatted-line">
 <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
 <link rel="match" href="text-box-trim-half-leading-block-box-003-ref.html">
 
@@ -17,6 +17,17 @@
 }
 </style>
 
+<!-- The SPANs here will be wrapped inside anonymous blocks. #div-parent will
+     thus start with an anonymous block (for the first SPAN). When looking for a
+     first formatted line, it will have to be inside this anonymous block (or it
+     doesn't exist at all).
+
+     To quote the spec:
+
+     The first formatted line of a block container [...] that contains
+     block-level content [...] is the first formatted line of its first in-flow
+     block-level child. If no such line exists, it has no first formatted
+     line. -->
 <div class="div-parent">
   <span>    </span>
   <div>Testline1<br>Testline2<br>Testline3</div>
diff --git a/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-006-ref.html b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-006-ref.html
new file mode 100644
index 00000000000000..6598123f1ae775
--- /dev/null
+++ b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-006-ref.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<title>Trimmed 3-line Reference</title>
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+
+<style>
+.div-parent {
+  outline: 1px solid orange;
+  font: 20px/1 Ahem;
+}
+</style>
+
+<div class="div-parent">
+  <div>Testline1<br><br><br>Testline2<br><br><br>Testline3<br></div>
+</div>
diff --git a/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-006.html b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-006.html
index ad6059ed7d89bb..244f5a1887aaea 100644
--- a/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-006.html
+++ b/css/css-inline/text-box-trim/text-box-trim-half-leading-block-box-006.html
@@ -3,7 +3,7 @@
 <link rel="help" href="https://drafts.csswg.org/css-inline-3/#text-box-trim">
 <link rel="help" href="https://www.w3.org/TR/css-inline-3/#invisible-line-boxes">
 <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
-<link rel="match" href="text-box-trim-half-leading-block-box-003-ref.html">
+<link rel="match" href="text-box-trim-half-leading-block-box-006-ref.html">
 
 <style>
 .div-parent {
diff --git a/css/css-inline/text-box-trim/text-box-trim-multicol-001-ref.html b/css/css-inline/text-box-trim/text-box-trim-multicol-001-ref.html
index aa81e23a26a490..c702c31d740601 100644
--- a/css/css-inline/text-box-trim/text-box-trim-multicol-001-ref.html
+++ b/css/css-inline/text-box-trim/text-box-trim-multicol-001-ref.html
@@ -26,5 +26,5 @@
   </span>
   abc abc abc abc
   abc abc
-  <div class="spacer up-half"></div>
+  <div class="spacer"></div>
 </div>
diff --git a/css/css-inline/text-box-trim/text-box-trim-multicol-002-ref.html b/css/css-inline/text-box-trim/text-box-trim-multicol-002-ref.html
new file mode 100644
index 00000000000000..aa81e23a26a490
--- /dev/null
+++ b/css/css-inline/text-box-trim/text-box-trim-multicol-002-ref.html
@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+<style>
+.spacer {
+  background: lightgray;
+  block-size: 100px;
+}
+.multicol {
+  column-count: 3;
+  column-fill: auto;
+  border: 1px solid;
+  height: 4lh;
+  width: 20ch;
+  font-family: Ahem;
+  font-size: 40px;
+  line-height: 2;
+}
+.up-half {
+  position: relative;
+  top: -20px;
+}
+</style>
+<div class="multicol">
+  <span class="up-half">
+    abc abc abc abc
+  </span>
+  abc abc abc abc
+  abc abc
+  <div class="spacer up-half"></div>
+</div>
diff --git a/css/css-inline/text-box-trim/text-box-trim-multicol-002.html b/css/css-inline/text-box-trim/text-box-trim-multicol-002.html
index 445814df90430c..1b6585590ef022 100644
--- a/css/css-inline/text-box-trim/text-box-trim-multicol-002.html
+++ b/css/css-inline/text-box-trim/text-box-trim-multicol-002.html
@@ -2,7 +2,7 @@
 <title>Test when a box with `text-box-trim` is block fragmented</title>
 <link rel="help" href="https://drafts.csswg.org/css-inline-3/#text-box-edge">
 <link rel="help" href="https://drafts.csswg.org/css-inline-3/#text-box-trim">
-<link rel="match" href="text-box-trim-multicol-001-ref.html">
+<link rel="match" href="text-box-trim-multicol-002-ref.html">
 <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
 <style>
 .spacer {
