diff --git a/components/style/gecko_bindings/sugar/ns_style_auto_array.rs b/components/style/gecko_bindings/sugar/ns_style_auto_array.rs
index 5730382d7d14..4ef12625d2d0 100644
--- a/components/style/gecko_bindings/sugar/ns_style_auto_array.rs
+++ b/components/style/gecko_bindings/sugar/ns_style_auto_array.rs
@@ -6,8 +6,22 @@
 
 use gecko_bindings::structs::nsStyleAutoArray;
 use std::iter::{once, Chain, Once, IntoIterator};
+use std::ops::Index;
 use std::slice::{Iter, IterMut};
 
+impl<T> Index<usize> for nsStyleAutoArray<T> {
+    type Output = T;
+    fn index(&self, index: usize) -> &T {
+        if index > self.len() {
+            panic!("out of range")
+        }
+        match index {
+            0 => &self.mFirstElement,
+            _ => &self.mOtherElements[index - 1],
+        }
+    }
+}
+
 impl<T> nsStyleAutoArray<T> {
     /// Mutably iterate over the array elements.
     pub fn iter_mut(&mut self) -> Chain<Once<&mut T>, IterMut<T>> {