diff --git a/gfx/2d/PathD2D.cpp b/gfx/2d/PathD2D.cpp
index c11f3566f8a7..de01b410a9bf 100644
--- a/gfx/2d/PathD2D.cpp
+++ b/gfx/2d/PathD2D.cpp
@@ -188,10 +188,10 @@ void PathBuilderD2D::Arc(const Point& aOrigin, Float aRadius, Float aStartAngle,
   // XXX - Workaround for now, D2D does not appear to do the desired thing when
   // the angle sweeps a complete circle.
   bool fullCircle = false;
-  if (aEndAngle - aStartAngle >= 2 * M_PI) {
+  if (aEndAngle - aStartAngle >= 1.9999 * M_PI) {
     fullCircle = true;
     aEndAngle = Float(aStartAngle + M_PI * 1.9999);
-  } else if (aStartAngle - aEndAngle >= 2 * M_PI) {
+  } else if (aStartAngle - aEndAngle >= 1.9999 * M_PI) {
     fullCircle = true;
     aStartAngle = Float(aEndAngle + M_PI * 1.9999);
   }
diff --git a/testing/web-platform/tests/html/canvas/element/path-objects/2d.path.arc.twopie.5.html b/testing/web-platform/tests/html/canvas/element/path-objects/2d.path.arc.twopie.5.html
new file mode 100644
index 000000000000..955a6c87436a
--- /dev/null
+++ b/testing/web-platform/tests/html/canvas/element/path-objects/2d.path.arc.twopie.5.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<!-- DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py. -->
+<title>Canvas test: 2d.path.arc.twopie.5</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/html/canvas/resources/canvas-tests.js"></script>
+<link rel="stylesheet" href="/html/canvas/resources/canvas-tests.css">
+<body class="show_output">
+
+<h1>2d.path.arc.twopie.5</h1>
+<p class="desc">arc() draws correctly when start = 2 and end = start + 2pi+e and clockwise</p>
+
+
+<p class="output">Actual output:</p>
+<canvas id="c" class="output" width="100" height="50"><p class="fallback">FAIL (fallback content)</p></canvas>
+
+<ul id="d"></ul>
+<script>
+var t = async_test("arc() draws correctly when start = 2 and end = start + 2pi+e and clockwise");
+_addTest(function(canvas, ctx) {
+
+  ctx.fillStyle = '#fff';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.fillStyle = '#000';
+  ctx.beginPath();
+  ctx.moveTo(50, 25);
+  ctx.arc(50, 25, 50, 2, 2 + 2*Math.PI, false);
+  ctx.closePath();
+  ctx.fill();
+  _assertPixel(canvas, 95,25, 0,0,0,255);
+
+});
+</script>
+
diff --git a/testing/web-platform/tests/html/canvas/element/path-objects/2d.path.arc.twopie.6.html b/testing/web-platform/tests/html/canvas/element/path-objects/2d.path.arc.twopie.6.html
new file mode 100644
index 000000000000..9420ecdc935b
--- /dev/null
+++ b/testing/web-platform/tests/html/canvas/element/path-objects/2d.path.arc.twopie.6.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<!-- DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py. -->
+<title>Canvas test: 2d.path.arc.twopie.6</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/html/canvas/resources/canvas-tests.js"></script>
+<link rel="stylesheet" href="/html/canvas/resources/canvas-tests.css">
+<body class="show_output">
+
+<h1>2d.path.arc.twopie.6</h1>
+<p class="desc">arc() draws correctly when start = 5 and end = start + 2pi+e and clockwise</p>
+
+
+<p class="output">Actual output:</p>
+<canvas id="c" class="output" width="100" height="50"><p class="fallback">FAIL (fallback content)</p></canvas>
+
+<ul id="d"></ul>
+<script>
+var t = async_test("arc() draws correctly when start = 5 and end = start + 2pi+e and clockwise");
+_addTest(function(canvas, ctx) {
+
+  ctx.fillStyle = '#fff';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.fillStyle = '#000';
+  ctx.beginPath();
+  ctx.moveTo(50, 25);
+  ctx.arc(50, 25, 50, 5, 5 + 2*Math.PI, false);
+  ctx.closePath();
+  ctx.fill();
+  _assertPixel(canvas, 5,25, 0,0,0,255);
+
+});
+</script>
+
diff --git a/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.5.html b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.5.html
new file mode 100644
index 000000000000..17c66c527c40
--- /dev/null
+++ b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.5.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<!-- DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py. -->
+<title>OffscreenCanvas test: 2d.path.arc.twopie.5</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/html/canvas/resources/canvas-tests.js"></script>
+
+<h1>2d.path.arc.twopie.5</h1>
+<p class="desc">arc() draws correctly when start = 2 and end = start + 2pi+e and clockwise</p>
+
+
+<script>
+var t = async_test("arc() draws correctly when start = 2 and end = start + 2pi+e and clockwise");
+var t_pass = t.done.bind(t);
+var t_fail = t.step_func(function(reason) {
+    throw reason;
+});
+t.step(function() {
+
+  var canvas = new OffscreenCanvas(100, 50);
+  var ctx = canvas.getContext('2d');
+
+  ctx.fillStyle = '#fff';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.fillStyle = '#000';
+  ctx.beginPath();
+  ctx.moveTo(50, 25);
+  ctx.arc(50, 25, 50, 2, 2 + 2*Math.PI, false);
+  ctx.closePath();
+  ctx.fill();
+  _assertPixel(canvas, 95,25, 0,0,0,255);
+  t.done();
+
+});
+</script>
diff --git a/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.5.worker.js b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.5.worker.js
new file mode 100644
index 000000000000..8fa29d5a9727
--- /dev/null
+++ b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.5.worker.js
@@ -0,0 +1,30 @@
+// DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py.
+// OffscreenCanvas test in a worker:2d.path.arc.twopie.5
+// Description:arc() draws correctly when start = 2 and end = start + 2pi+e and clockwise
+// Note:
+
+importScripts("/resources/testharness.js");
+importScripts("/html/canvas/resources/canvas-tests.js");
+
+var t = async_test("arc() draws correctly when start = 2 and end = start + 2pi+e and clockwise");
+var t_pass = t.done.bind(t);
+var t_fail = t.step_func(function(reason) {
+    throw reason;
+});
+t.step(function() {
+
+  var canvas = new OffscreenCanvas(100, 50);
+  var ctx = canvas.getContext('2d');
+
+  ctx.fillStyle = '#fff';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.fillStyle = '#000';
+  ctx.beginPath();
+  ctx.moveTo(50, 25);
+  ctx.arc(50, 25, 50, 2, 2 + 2*Math.PI, false);
+  ctx.closePath();
+  ctx.fill();
+  _assertPixel(canvas, 95,25, 0,0,0,255);
+  t.done();
+});
+done();
diff --git a/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.6.html b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.6.html
new file mode 100644
index 000000000000..befec827044c
--- /dev/null
+++ b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.6.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<!-- DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py. -->
+<title>OffscreenCanvas test: 2d.path.arc.twopie.6</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/html/canvas/resources/canvas-tests.js"></script>
+
+<h1>2d.path.arc.twopie.6</h1>
+<p class="desc">arc() draws correctly when start = 5 and end = start + 2pi+e and clockwise</p>
+
+
+<script>
+var t = async_test("arc() draws correctly when start = 5 and end = start + 2pi+e and clockwise");
+var t_pass = t.done.bind(t);
+var t_fail = t.step_func(function(reason) {
+    throw reason;
+});
+t.step(function() {
+
+  var canvas = new OffscreenCanvas(100, 50);
+  var ctx = canvas.getContext('2d');
+
+  ctx.fillStyle = '#fff';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.fillStyle = '#000';
+  ctx.beginPath();
+  ctx.moveTo(50, 25);
+  ctx.arc(50, 25, 50, 5, 5 + 2*Math.PI, false);
+  ctx.closePath();
+  ctx.fill();
+  _assertPixel(canvas, 5,25, 0,0,0,255);
+  t.done();
+
+});
+</script>
diff --git a/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.6.worker.js b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.6.worker.js
new file mode 100644
index 000000000000..546cbce33c02
--- /dev/null
+++ b/testing/web-platform/tests/html/canvas/offscreen/path-objects/2d.path.arc.twopie.6.worker.js
@@ -0,0 +1,30 @@
+// DO NOT EDIT! This test has been generated by /html/canvas/tools/gentest.py.
+// OffscreenCanvas test in a worker:2d.path.arc.twopie.6
+// Description:arc() draws correctly when start = 5 and end = start + 2pi+e and clockwise
+// Note:
+
+importScripts("/resources/testharness.js");
+importScripts("/html/canvas/resources/canvas-tests.js");
+
+var t = async_test("arc() draws correctly when start = 5 and end = start + 2pi+e and clockwise");
+var t_pass = t.done.bind(t);
+var t_fail = t.step_func(function(reason) {
+    throw reason;
+});
+t.step(function() {
+
+  var canvas = new OffscreenCanvas(100, 50);
+  var ctx = canvas.getContext('2d');
+
+  ctx.fillStyle = '#fff';
+  ctx.fillRect(0, 0, 100, 50);
+  ctx.fillStyle = '#000';
+  ctx.beginPath();
+  ctx.moveTo(50, 25);
+  ctx.arc(50, 25, 50, 5, 5 + 2*Math.PI, false);
+  ctx.closePath();
+  ctx.fill();
+  _assertPixel(canvas, 5,25, 0,0,0,255);
+  t.done();
+});
+done();
diff --git a/testing/web-platform/tests/html/canvas/tools/gentest.py b/testing/web-platform/tests/html/canvas/tools/gentest.py
index 6574ff532383..36cb7fe0f6cd 100644
--- a/testing/web-platform/tests/html/canvas/tools/gentest.py
+++ b/testing/web-platform/tests/html/canvas/tools/gentest.py
@@ -1,3 +1,13 @@
+# To use this script:
+# -make a python virtual environment somewhere (it doesn't matter where)
+#   python3 -m venv venv
+# -enter the virtual environment
+#   source venv/bin/activate
+# -install required packages in the venv
+#   pip3 install cairocffi jinja2 pyyaml
+# -change to the directory with this script and run it
+#   python3 gentest.py
+
 from gentestutils import genTestUtils
 from gentestutilsunion import genTestUtils_union
 
diff --git a/testing/web-platform/tests/html/canvas/tools/yaml-new/path-objects.yaml b/testing/web-platform/tests/html/canvas/tools/yaml-new/path-objects.yaml
index eec142c7692b..673c90857442 100644
--- a/testing/web-platform/tests/html/canvas/tools/yaml-new/path-objects.yaml
+++ b/testing/web-platform/tests/html/canvas/tools/yaml-new/path-objects.yaml
@@ -966,6 +966,32 @@
     @assert pixel 50,20 == 0,255,0,255;
   expected: green
 
+- name: 2d.path.arc.twopie.5
+  desc: arc() draws correctly when start = 2 and end = start + 2pi+e and clockwise
+  code: |
+    ctx.fillStyle = '#fff';
+    ctx.fillRect(0, 0, 100, 50);
+    ctx.fillStyle = '#000';
+    ctx.beginPath();
+    ctx.moveTo(50, 25);
+    ctx.arc(50, 25, 50, 2, 2 + 2*Math.PI, false);
+    ctx.closePath();
+    ctx.fill();
+    @assert pixel 95,25 == 0,0,0,255;
+
+- name: 2d.path.arc.twopie.6
+  desc: arc() draws correctly when start = 5 and end = start + 2pi+e and clockwise
+  code: |
+    ctx.fillStyle = '#fff';
+    ctx.fillRect(0, 0, 100, 50);
+    ctx.fillStyle = '#000';
+    ctx.beginPath();
+    ctx.moveTo(50, 25);
+    ctx.arc(50, 25, 50, 5, 5 + 2*Math.PI, false);
+    ctx.closePath();
+    ctx.fill();
+    @assert pixel 5,25 == 0,0,0,255;
+
 - name: 2d.path.arc.shape.1
   desc: arc() from 0 to pi does not draw anything in the wrong half
   code: |
