--- a/testing/web-platform/tests/web-animations/animation-model/animation-types/property-list.js
+++ b/testing/web-platform/tests/web-animations/animation-model/animation-types/property-list.js
@@ -466,18 +466,17 @@ var gCSSProperties = {
   },
   'fill': {
     // https://svgwg.org/svg2-draft/painting.html#FillProperty
     types: [
     ]
   },
   'fill-opacity': {
     // https://svgwg.org/svg2-draft/painting.html#FillOpacityProperty
-    types: [
-    ]
+    types: [ 'opacity' ]
   },
   'fill-rule': {
     // https://svgwg.org/svg2-draft/painting.html#FillRuleProperty
     types: [
       { type: 'discrete', options: [ [ 'evenodd', 'nonzero' ] ] }
     ]
   },
   'filter': {