diff --git a/components/style/gecko_bindings/bindings.rs b/components/style/gecko_bindings/bindings.rs
index b16d0a442b3..034992d1b21 100644
--- a/components/style/gecko_bindings/bindings.rs
+++ b/components/style/gecko_bindings/bindings.rs
@@ -1301,6 +1301,11 @@ extern "C" {
                                                RawServoAnimationValueBorrowedListBorrowed)
      -> RawServoDeclarationBlockStrong;
 }
+extern "C" {
+    pub fn Servo_AnimationValues_GetOpacity(value:
+                                                RawServoAnimationValueBorrowed)
+     -> f32;
+}
 extern "C" {
     pub fn Servo_ParseStyleAttribute(data: *const nsACString_internal)
      -> RawServoDeclarationBlockStrong;
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index d53c72d3e8c..bee77e36b9f 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -205,6 +205,18 @@ pub extern "C" fn Servo_AnimationValues_Uncompute(value: RawServoAnimationValueB
     })).into_strong()
 }
 
+#[no_mangle]
+pub extern "C" fn Servo_AnimationValues_GetOpacity(value: RawServoAnimationValueBorrowed)
+     -> f32
+{
+    let value = AnimationValue::as_arc(&value);
+    if let AnimationValue::Opacity(opacity) = **value {
+        opacity
+    } else {
+        panic!("The AnimationValue should be Opacity");
+    }
+}
+
 /// Takes a ServoAnimationValues and populates it with the animation values corresponding
 /// to a given property declaration block
 #[no_mangle]