diff --git a/components/style/properties/longhand/svg.mako.rs b/components/style/properties/longhand/svg.mako.rs
index 16e884d8227..4309926a99c 100644
--- a/components/style/properties/longhand/svg.mako.rs
+++ b/components/style/properties/longhand/svg.mako.rs
@@ -13,6 +13,14 @@ ${helpers.single_keyword("dominant-baseline",
 
 ${helpers.single_keyword("vector-effect", "none non-scaling-stroke", products="gecko")}
 
+// Section 13 - Gradients and Patterns
+
+${helpers.predefined_type("stop-opacity", "Opacity", "1.0", products="gecko")}
+
+// Section 15 - Filter Effects
+
+${helpers.predefined_type("flood-opacity", "Opacity", "1.0", products="gecko")}
+
 // CSS Masking Module Level 1
 // https://www.w3.org/TR/css-masking-1/
 ${helpers.single_keyword("mask-type", "luminance alpha", products="gecko")}
diff --git a/components/style/properties/longhand/svg_inherited.mako.rs b/components/style/properties/longhand/svg_inherited.mako.rs
index a2c2be61fb4..29dd27a7615 100644
--- a/components/style/properties/longhand/svg_inherited.mako.rs
+++ b/components/style/properties/longhand/svg_inherited.mako.rs
@@ -22,6 +22,8 @@ ${helpers.single_keyword("color-interpolation-filters",
                          products="gecko",
                          gecko_constant_prefix="NS_STYLE_COLOR_INTERPOLATION")}
 
+${helpers.predefined_type("fill-opacity", "Opacity", "1.0", products="gecko")}
+
 ${helpers.single_keyword("fill-rule", "nonzero evenodd", products="gecko")}
 
 ${helpers.single_keyword("shape-rendering",
@@ -32,6 +34,8 @@ ${helpers.single_keyword("stroke-linecap", "butt round square", products="gecko"
 
 ${helpers.single_keyword("stroke-linejoin", "miter round bevel", products="gecko")}
 
+${helpers.predefined_type("stroke-opacity", "Opacity", "1.0", products="gecko")}
+
 // Section 14 - Clipping, Masking and Compositing
 ${helpers.single_keyword("clip-rule", "nonzero evenodd",
                          products="gecko",