diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index 834e9606c49..d70cc85fe85 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -1019,10 +1019,14 @@ impl<'a> CanvasRenderingContext2DMethods for &'a CanvasRenderingContext2D {
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-createradialgradient
     fn CreateRadialGradient(self, x0: Finite<f64>, y0: Finite<f64>, r0: Finite<f64>,
                             x1: Finite<f64>, y1: Finite<f64>, r1: Finite<f64>)
-                            -> Root<CanvasGradient> {
-        CanvasGradient::new(self.global.root().r(),
-                            CanvasGradientStyle::Radial(
-                                RadialGradientStyle::new(*x0, *y0, *r0, *x1, *y1, *r1, Vec::new())))
+                            -> Fallible<Root<CanvasGradient>> {
+        if *r0 < 0. || *r1 < 0. {
+            return Err(IndexSize);
+        }
+
+        Ok(CanvasGradient::new(self.global.root().r(),
+                               CanvasGradientStyle::Radial(
+                                   RadialGradientStyle::new(*x0, *y0, *r0, *x1, *y1, *r1, Vec::new()))))
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-createpattern
diff --git a/components/script/dom/webidls/CanvasRenderingContext2D.webidl b/components/script/dom/webidls/CanvasRenderingContext2D.webidl
index 251daaac846..295fc2fb3b7 100644
--- a/components/script/dom/webidls/CanvasRenderingContext2D.webidl
+++ b/components/script/dom/webidls/CanvasRenderingContext2D.webidl
@@ -59,6 +59,7 @@ interface CanvasRenderingContext2D {
            attribute (DOMString or CanvasGradient or CanvasPattern) strokeStyle; // (default black)
            attribute (DOMString or CanvasGradient or CanvasPattern) fillStyle; // (default black)
   CanvasGradient createLinearGradient(double x0, double y0, double x1, double y1);
+  [Throws]
   CanvasGradient createRadialGradient(double x0, double y0, double r0, double x1, double y1, double r1);
   [Throws]
   CanvasPattern createPattern(CanvasImageSource image, [TreatNullAs=EmptyString] DOMString repetition);
diff --git a/tests/wpt/metadata/2dcontext/fill-and-stroke-styles/2d.gradient.radial.negative.html.ini b/tests/wpt/metadata/2dcontext/fill-and-stroke-styles/2d.gradient.radial.negative.html.ini
deleted file mode 100644
index e7b491b0005..00000000000
--- a/tests/wpt/metadata/2dcontext/fill-and-stroke-styles/2d.gradient.radial.negative.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[2d.gradient.radial.negative.html]
-  type: testharness
-  [createRadialGradient() throws INDEX_SIZE_ERR if either radius is negative]
-    expected: FAIL
-