diff --git a/layout/tables/nsTableFrame.cpp b/layout/tables/nsTableFrame.cpp
index 0129c749360a790cf6f4e6aa30a9577b3f9bedaf..e932f2b98c2787c51d5a55a34d7d9cd290b7ea47 100644
--- a/layout/tables/nsTableFrame.cpp
+++ b/layout/tables/nsTableFrame.cpp
@@ -7285,6 +7285,22 @@ void BCPaintBorderIterator::AccumulateOrDoActionBlockDirSegment(
}
}
blockDirSeg.AdvanceOffsetB();
+ // If the row is empty and cell borders are defined, the row will be
+ // zero-sized (If there existed an empty cell, it'd be sized to contain
+ // the cell's borders). In this case, we effectively need to "pull up"
+ // where the segment starts (Unless the empty row has enough block size).
+ if (mRow->PrincipalChildList().IsEmpty()) {
+ const auto rowSize = mRow->BSize(mTableWM);
+ if (blockDirSeg.mBEndOffset > 0 && blockDirSeg.mBEndOffset > rowSize) {
+ blockDirSeg.mOffsetB -= blockDirSeg.mBEndOffset - rowSize;
+ } else if (blockDirSeg.mBEndOffset < 0 &&
+ -blockDirSeg.mBEndOffset > rowSize) {
+ // For cases of segments that don't have bevel (e.g. inner block
+ // direction borders). Since they "end early," the block end offset is
+ // negative.
+ blockDirSeg.mOffsetB += blockDirSeg.mBEndOffset + rowSize;
+ }
+ }
}
blockDirSeg.Start(*this, borderOwner, blockSegISize, inlineSegBSize);
}
diff --git a/testing/web-platform/tests/css/CSS2/tables/border-collapse-empty-row-ref.html b/testing/web-platform/tests/css/CSS2/tables/border-collapse-empty-row-ref.html
new file mode 100644
index 0000000000000000000000000000000000000000..ca1108ccd7bf733e26e3bb6f9105404063da942a
--- /dev/null
+++ b/testing/web-platform/tests/css/CSS2/tables/border-collapse-empty-row-ref.html
@@ -0,0 +1,69 @@
+<!DOCTYPE html>
+<link rel="author" title="David Shin" href="mailto:dshin@mozilla.com">
+<link rel="help" href="http://www.w3.org/TR/CSS21/tables.html#collapsing-borders">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1819266">
+<meta name="assert" content="This test checks that collapsed border does not paint outside of its expected area.">
+<style>
+table {
+ display: inline-table;
+ border-collapse: collapse;
+}
+
+td {
+ border: 10px solid black;
+ line-height: 0;
+ padding: 0;
+}
+
+span {
+ display: inline-block;
+ width: 10px;
+ height: 10px;
+ background: grey;
+}
+
+.spacer-1 tr:not(:last-child) td {
+ border-bottom: 12px solid black;
+}
+
+.spacer-2 tr:not(:last-child) td {
+ border-bottom: 15px solid black;
+}
+
+.spacer-3 tr:not(:last-child) td {
+ border-bottom: 20px solid black;
+}
+
+</style>
+<table>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>
+<table class="spacer-1">
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>
+<table class="spacer-2">
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>
+<table class="spacer-3">
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>
diff --git a/testing/web-platform/tests/css/CSS2/tables/border-collapse-empty-row.html b/testing/web-platform/tests/css/CSS2/tables/border-collapse-empty-row.html
new file mode 100644
index 0000000000000000000000000000000000000000..c4114a145df0c18ee6745c3cb3e74388609a9eb9
--- /dev/null
+++ b/testing/web-platform/tests/css/CSS2/tables/border-collapse-empty-row.html
@@ -0,0 +1,93 @@
+<!DOCTYPE html>
+<link rel="author" title="David Shin" href="mailto:dshin@mozilla.com">
+<link rel="help" href="http://www.w3.org/TR/CSS21/tables.html#collapsing-borders">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1819266">
+<link rel="match" href="border-collapse-empty-row-ref.html">
+<meta name="assert" content="This test checks that collapsed border does not paint outside of its expected area.">
+<style>
+table {
+ display: inline-table;
+ border-collapse: collapse;
+}
+
+td {
+ border: 10px solid black;
+ line-height: 0;
+ padding: 0;
+}
+
+span {
+ display: inline-block;
+ width: 10px;
+ height: 10px;
+ background: grey;
+}
+
+.spacer-1 {
+ height: 2px;
+}
+
+.spacer-2 {
+ height: 5px;
+}
+
+.spacer-3 {
+ height: 10px;
+}
+</style>
+<!-- Empty rows -->
+<table>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>
+<!-- Empty rows, sized less than collapsed border offset (10px / 2 = 5px). -->
+<table>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-1"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-1"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-1"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-1"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-1"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>
+<!-- Empty rows, sized exactly at collapsed border offset. -->
+<table>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-2"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-2"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-2"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-2"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-2"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>
+<!-- Empty rows, sized larger than collapsed border offset. -->
+<table>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-3"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-3"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-3"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-3"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+<tr class="spacer-3"></tr>
+<tr><td><span></span></td><td><span></span></td></tr>
+</table>