diff --git a/components/layout/display_list/background.rs b/components/layout/display_list/background.rs
index e167df9cc4b..1aa8e86453e 100644
--- a/components/layout/display_list/background.rs
+++ b/components/layout/display_list/background.rs
@@ -19,9 +19,11 @@ use model::{self, MaybeAuto};
 use style::computed_values::background_attachment::single_value::T as BackgroundAttachment;
 use style::computed_values::background_clip::single_value::T as BackgroundClip;
 use style::computed_values::background_origin::single_value::T as BackgroundOrigin;
+use style::computed_values::border_image_outset::T as BorderImageOutset;
 use style::properties::style_structs::{self, Background};
+use style::values::Either;
 use style::values::computed::{Angle, GradientItem};
-use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto};
+use style::values::computed::{LengthOrNumber, LengthOrPercentage, LengthOrPercentageOrAuto};
 use style::values::computed::{NumberOrPercentage, Percentage, Position};
 use style::values::computed::image::{EndingShape, LineDirection};
 use style::values::generics::background::BackgroundSize;
@@ -784,6 +786,7 @@ pub fn calculate_inner_border_radii(
 pub fn build_image_border_details(
     webrender_image: WebRenderImageInfo,
     border_style_struct: &style_structs::Border,
+    outset: SideOffsets2D<f32>,
 ) -> Option<BorderDetails> {
     let corners = &border_style_struct.border_image_slice.offsets;
     let border_image_repeat = &border_style_struct.border_image_repeat;
@@ -801,8 +804,7 @@ pub fn build_image_border_details(
                 ),
             },
             fill: border_style_struct.border_image_slice.fill,
-            // TODO(gw): Support border-image-outset
-            outset: SideOffsets2D::zero(),
+            outset: outset,
             repeat_horizontal: border_image_repeat.0.to_layout(),
             repeat_vertical: border_image_repeat.1.to_layout(),
         }))
@@ -810,3 +812,25 @@ pub fn build_image_border_details(
         None
     }
 }
+
+fn calculate_border_image_outset_side(
+    outset: LengthOrNumber,
+    border_width: Au,
+) -> Au {
+    match outset {
+        Either::First(length) => length.into(),
+        Either::Second(factor) => border_width.scale_by(factor),
+    }
+}
+
+pub fn calculate_border_image_outset(
+    outset: BorderImageOutset,
+    border: SideOffsets2D<Au>,
+) -> SideOffsets2D<Au> {
+    SideOffsets2D::new(
+        calculate_border_image_outset_side(outset.0, border.top),
+        calculate_border_image_outset_side(outset.1, border.right),
+        calculate_border_image_outset_side(outset.2, border.bottom),
+        calculate_border_image_outset_side(outset.3, border.left),
+    )
+}
diff --git a/components/layout/display_list/builder.rs b/components/layout/display_list/builder.rs
index 0860a6f61a0..1d36ab26052 100644
--- a/components/layout/display_list/builder.rs
+++ b/components/layout/display_list/builder.rs
@@ -16,9 +16,9 @@ use canvas_traits::canvas::{CanvasMsg, FromLayoutMsg};
 use context::LayoutContext;
 use display_list::ToLayout;
 use display_list::background::{build_border_radius, build_image_border_details};
-use display_list::background::{calculate_inner_border_radii, compute_background_placement};
-use display_list::background::{convert_linear_gradient, convert_radial_gradient};
-use display_list::background::{get_cyclic, simple_normal_border};
+use display_list::background::{calculate_border_image_outset, calculate_inner_border_radii};
+use display_list::background::{compute_background_placement, convert_linear_gradient};
+use display_list::background::{convert_radial_gradient, get_cyclic, simple_normal_border};
 use display_list::items::{BaseDisplayItem, BorderDetails, BorderDisplayItem, BLUR_INFLATION_FACTOR};
 use display_list::items::{BoxShadowDisplayItem, ClipScrollNode};
 use display_list::items::{ClipScrollNodeIndex, ClipScrollNodeType, ClippingAndScrolling};
@@ -1264,6 +1264,18 @@ impl FragmentDisplayListBuilding for Fragment {
         );
 
         let border_radius = build_border_radius(&bounds, border_style_struct);
+        let border_widths = border.to_physical(style.writing_mode);
+        let outset = calculate_border_image_outset(
+            border_style_struct.border_image_outset,
+            border_widths
+        );
+        let outset_layout = SideOffsets2D::new(
+            outset.top.to_f32_px(),
+            outset.right.to_f32_px(),
+            outset.bottom.to_f32_px(),
+            outset.left.to_f32_px(),
+        );
+        let size = bounds.outer_rect(outset).size;
 
         let details = match border_style_struct.border_image_source {
             Either::First(_) => Some(BorderDetails::Normal(NormalBorder {
@@ -1295,8 +1307,7 @@ impl FragmentDisplayListBuilding for Fragment {
                                 angle_or_corner,
                                 gradient.repeating,
                             ),
-                            // TODO(gw): Support border-image-outset
-                            outset: SideOffsets2D::zero(),
+                            outset: outset_layout,
                         })
                     },
                     GradientKind::Radial(shape, center, _angle) => {
@@ -1308,17 +1319,14 @@ impl FragmentDisplayListBuilding for Fragment {
                                 center,
                                 gradient.repeating,
                             ),
-                            // TODO(gw): Support border-image-outset
-                            outset: SideOffsets2D::zero(),
+                            outset: outset_layout,
                         })
                     },
                 })
             },
             Either::Second(Image::PaintWorklet(ref paint_worklet)) => {
-                // TODO: this size should be increased by border-image-outset
-                let size = self.border_box.size.to_physical(style.writing_mode);
                 self.get_webrender_image_for_paint_worklet(state, style, paint_worklet, size)
-                    .and_then(|image| build_image_border_details(image, border_style_struct))
+                    .and_then(|image| build_image_border_details(image, border_style_struct, outset_layout))
             },
             Either::Second(Image::Rect(..)) => {
                 // TODO: Handle border-image with `-moz-image-rect`.
@@ -1337,12 +1345,12 @@ impl FragmentDisplayListBuilding for Fragment {
                         UsePlaceholder::No,
                     )
                 })
-                .and_then(|image| build_image_border_details(image, border_style_struct)),
+                .and_then(|image| build_image_border_details(image, border_style_struct, outset_layout)),
         };
         if let Some(details) = details {
             state.add_display_item(DisplayItem::Border(Box::new(BorderDisplayItem {
                 base,
-                border_widths: border.to_physical(style.writing_mode).to_layout(),
+                border_widths: border_widths.to_layout(),
                 details,
             })));
         }
diff --git a/tests/wpt/metadata/MANIFEST.json b/tests/wpt/metadata/MANIFEST.json
index c9e1fa74b2e..570ee11f310 100644
--- a/tests/wpt/metadata/MANIFEST.json
+++ b/tests/wpt/metadata/MANIFEST.json
@@ -103651,6 +103651,18 @@
      {}
     ]
    ],
+   "css/css-backgrounds/border-image-outset-003.html": [
+    [
+     "/css/css-backgrounds/border-image-outset-003.html",
+     [
+      [
+       "/css/css-backgrounds/border-image-outset-003-ref.html",
+       "=="
+      ]
+     ],
+     {}
+    ]
+   ],
    "css/css-backgrounds/border-image-repeat-round.html": [
     [
      "/css/css-backgrounds/border-image-repeat-round.html",
@@ -238780,6 +238792,11 @@
      {}
     ]
    ],
+   "css/css-backgrounds/border-image-outset-003-ref.html": [
+    [
+     {}
+    ]
+   ],
    "css/css-backgrounds/border-radius-001-ref.xht": [
     [
      {}
@@ -490958,13 +490975,21 @@
    "visual"
   ],
   "css/css-backgrounds/border-image-outset-001.htm": [
-   "91206118ea44913c07090d59a2a702b8ba3fb6ef",
+   "796f739d337c442e64c13ffedc25b38c017ac48d",
    "visual"
   ],
   "css/css-backgrounds/border-image-outset-002.htm": [
-   "6101a51156146dec7d46599f7b8dc34934d9ea2f",
+   "9e79efb85575ddc330b69a13265a44bc18723dbd",
    "visual"
   ],
+  "css/css-backgrounds/border-image-outset-003-ref.html": [
+   "2679f735e348a77aecd49a1f35794e9fc3a9dd87",
+   "support"
+  ],
+  "css/css-backgrounds/border-image-outset-003.html": [
+   "378c9808884010c2e0b0226552b519f3ab4cedce",
+   "reftest"
+  ],
   "css/css-backgrounds/border-image-repeat-001.htm": [
    "62ebca7169dbd69684405ec03f86d720fc3354b7",
    "visual"
diff --git a/tests/wpt/metadata/css/css-backgrounds/background-size-025.html.ini b/tests/wpt/metadata/css/css-backgrounds/background-size-025.html.ini
deleted file mode 100644
index 4143512af62..00000000000
--- a/tests/wpt/metadata/css/css-backgrounds/background-size-025.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[background-size-025.html]
-  expected: FAIL
diff --git a/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-001.htm b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-001.htm
index 232fd74c3f3..db0a8f5f6bb 100644
Binary files a/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-001.htm and b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-001.htm differ
diff --git a/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-002.htm b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-002.htm
index ce20a5b5ffc..d8fbf944b81 100644
Binary files a/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-002.htm and b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-002.htm differ
diff --git a/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-003-ref.html b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-003-ref.html
new file mode 100644
index 00000000000..4d55cddd1cc
--- /dev/null
+++ b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-003-ref.html
@@ -0,0 +1,23 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Blue Box with Green Frame</title>
+<style>
+    #a {
+        width: 300px;
+        height: 200px;
+        position: absolute;
+        left: 100px;
+        top: 100px;
+        border-width: 50px;
+        border-style: solid;
+        border-image: linear-gradient(green, green);
+        background-color: blue;
+        background-clip: content-box;
+        border-image-slice: 33%;
+        padding-left: 100px;
+        padding-top: 50px;
+        padding-right: 10px;
+        padding-bottom: 50px;
+    }
+</style>
+<div id="a"></div>
\ No newline at end of file
diff --git a/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-003.html b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-003.html
new file mode 100644
index 00000000000..27bc02682ca
--- /dev/null
+++ b/tests/wpt/web-platform-tests/css/css-backgrounds/border-image-outset-003.html
@@ -0,0 +1,22 @@
+<!doctype html>
+<meta charset="utf-8">
+<title>Background Image Outset</title>
+<link rel="match" href="border-image-outset-003-ref.html">
+<link rel="help" href="https://drafts.csswg.org/css-backgrounds-3/#border-image-outset" />
+<style>
+    #a {
+        width: 300px;
+        height: 200px;
+        position: absolute;
+        left: 200px;
+        top: 150px;
+        border-width: 50px;
+        border-style: solid;
+        border-image: linear-gradient(green, green);
+        background-color: blue;
+        background-clip: content-box;
+        border-image-outset: 50px 10px 50px 100px;
+        border-image-slice: 33%;
+    }
+</style>
+<div id="a"></div>
\ No newline at end of file