diff --git a/webrender/src/clip.rs b/webrender/src/clip.rs
index ce59bd392c..24a3e7f1b5 100644
--- a/webrender/src/clip.rs
+++ b/webrender/src/clip.rs
@@ -10,7 +10,7 @@ use freelist::{FreeList, FreeListHandle, WeakFreeListHandle};
 use gpu_cache::{GpuCache, GpuCacheHandle, ToGpuBlocks};
 use prim_store::{ClipData, ImageMaskData};
 use resource_cache::ResourceCache;
-use util::{MaxRect, calculate_screen_bounding_rect, extract_inner_rect_safe};
+use util::{MaxRect, calculate_screen_inner_rect, calculate_screen_bounding_rect, extract_inner_rect_safe};
 
 pub type ClipStore = FreeList<ClipSources>;
 pub type ClipSourcesHandle = FreeListHandle<ClipSources>;
@@ -252,7 +252,7 @@ impl ClipSources {
         device_pixel_ratio: f32,
     ) -> (DeviceIntRect, Option<DeviceIntRect>) {
         let screen_inner_rect =
-            calculate_screen_bounding_rect(transform, &self.local_inner_rect, device_pixel_ratio);
+            calculate_screen_inner_rect(transform, &self.local_inner_rect, device_pixel_ratio);
         let screen_outer_rect = self.local_outer_rect.map(|outer_rect|
             calculate_screen_bounding_rect(transform, &outer_rect, device_pixel_ratio)
         );
diff --git a/webrender/src/util.rs b/webrender/src/util.rs
index e3e9ea73cc..b6252883f5 100644
--- a/webrender/src/util.rs
+++ b/webrender/src/util.rs
@@ -4,11 +4,11 @@
 
 use api::{BorderRadius, DeviceIntPoint, DeviceIntRect, DeviceIntSize, DevicePoint, DeviceRect};
 use api::{DeviceSize, LayerPoint, LayerRect, LayerSize, LayerToWorldTransform, WorldRect};
-use euclid::{Point2D, Rect, Size2D, TypedPoint2D, TypedRect, TypedSize2D, TypedTransform2D};
-use euclid::TypedTransform3D;
+use euclid::{Point2D, Rect, ScaleFactor, Size2D, TypedPoint2D, TypedRect, TypedSize2D};
+use euclid::{TypedTransform2D, TypedTransform3D};
 use num_traits::Zero;
-use std::i32;
-use std::f32;
+use std::{i32, f32};
+use std::cmp::Ordering;
 
 // Matches the definition of SK_ScalarNearlyZero in Skia.
 const NEARLY_ZERO: f32 = 1.0 / 4096.0;
@@ -143,20 +143,52 @@ pub fn calculate_screen_bounding_rect(
     rect: &LayerRect,
     device_pixel_ratio: f32
 ) -> DeviceIntRect {
-    let rect = WorldRect::from_points(&[
+    let points = [
         transform.transform_point2d(&rect.origin),
         transform.transform_point2d(&rect.top_right()),
         transform.transform_point2d(&rect.bottom_left()),
         transform.transform_point2d(&rect.bottom_right()),
-    ]) * device_pixel_ratio;
+    ];
+
+    let scale = ScaleFactor::new(device_pixel_ratio);
+    let rect: DeviceRect = WorldRect::from_points(&points) * scale;
+
+    let max_rect = DeviceRect::max_rect();
+    rect
+        .round_out()
+        .intersection(&max_rect)
+        .unwrap_or(max_rect)
+        .to_i32()
+}
+
+pub fn calculate_screen_inner_rect(
+    transform: &LayerToWorldTransform,
+    rect: &LayerRect,
+    device_pixel_ratio: f32
+) -> DeviceIntRect {
+    let points = [
+        transform.transform_point2d(&rect.origin),
+        transform.transform_point2d(&rect.top_right()),
+        transform.transform_point2d(&rect.bottom_left()),
+        transform.transform_point2d(&rect.bottom_right()),
+    ];
+    let mut xs = [points[0].x, points[1].x, points[2].x, points[3].x];
+    let mut ys = [points[0].y, points[1].y, points[2].y, points[3].y];
+
+    xs.sort_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal));
+    ys.sort_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal));
 
     let rect = DeviceRect::new(
-        DevicePoint::new(rect.origin.x, rect.origin.y),
-        DeviceSize::new(rect.size.width, rect.size.height),
-    );
+        DevicePoint::new(xs[1], ys[1]),
+        DeviceSize::new(xs[2] - xs[1], ys[2] - ys[1]),
+    ) * device_pixel_ratio;
 
     let max_rect = DeviceRect::max_rect();
-    rect.round_out().intersection(&max_rect).unwrap_or(max_rect).to_i32()
+    rect
+        .intersection(&max_rect)
+        .unwrap_or(max_rect)
+        .round_in()
+        .to_i32()
 }
 
 pub fn _subtract_rect<U>(
diff --git a/wrench/reftests/clip/clip-45-degree-rotation-ref.png b/wrench/reftests/clip/clip-45-degree-rotation-ref.png
new file mode 100644
index 0000000000..5a5e9ac10b
Binary files /dev/null and b/wrench/reftests/clip/clip-45-degree-rotation-ref.png differ
diff --git a/wrench/reftests/clip/clip-45-degree-rotation.yaml b/wrench/reftests/clip/clip-45-degree-rotation.yaml
new file mode 100644
index 0000000000..04cfed5a29
--- /dev/null
+++ b/wrench/reftests/clip/clip-45-degree-rotation.yaml
@@ -0,0 +1,35 @@
+# Test that transformed content is clipped properly by clips with a different transform.
+---
+root:
+  items:
+    -
+      bounds: [0, 0, 0, 0]
+      "clip-rect": [0, 0, 0, 0]
+      "clip-and-scroll": 0
+      type: "stacking-context"
+      transform: rotate(45) translate(200, 0)
+      items:
+        -
+          bounds: [0, 0, 300, 300]
+          "clip-rect": [0, 0, 300, 300]
+          "clip-and-scroll": 0
+          type: rect
+          color: red
+        -
+          bounds: [0, 0, 300, 300]
+          "clip-rect": [0, 0, 300, 300]
+          "clip-and-scroll": 0
+          type: clip
+          id: 5
+        -
+          bounds: [0, 0, 0, 0]
+          "clip-rect": [0, 0, 0, 0]
+          "clip-and-scroll": 5
+          type: "stacking-context"
+          transform: rotate(-45) translate(-300, 0)
+          items:
+            -
+              bounds: [0, 0, 1598, 1200]
+              "clip-rect": [0, 0, 1598, 1200]
+              type: rect
+              color: green
diff --git a/wrench/reftests/clip/reftest.list b/wrench/reftests/clip/reftest.list
index 54a7e7337d..c414cde627 100644
--- a/wrench/reftests/clip/reftest.list
+++ b/wrench/reftests/clip/reftest.list
@@ -1,3 +1,3 @@
 == clip-mode.yaml clip-mode.png
 == clip-ellipse.yaml clip-ellipse.png
-
+== clip-45-degree-rotation.yaml clip-45-degree-rotation-ref.png