diff --git a/components/style/data.rs b/components/style/data.rs
index 6c02f54305d..f1b92fae139 100644
--- a/components/style/data.rs
+++ b/components/style/data.rs
@@ -239,7 +239,7 @@ impl ElementData {
         element: E,
         shared_context: &SharedStyleContext,
         stack_limit_checker: Option<&StackLimitChecker>,
-        nth_index_cache: Option<&mut NthIndexCache>,
+        nth_index_cache: &mut NthIndexCache,
     ) -> InvalidationResult {
         // In animation-only restyle we shouldn't touch snapshot at all.
         if shared_context.traversal_flags.for_animation_only() {
diff --git a/components/style/invalidation/element/collector.rs b/components/style/invalidation/element/collector.rs
index 49430fd1b13..600d26757e2 100644
--- a/components/style/invalidation/element/collector.rs
+++ b/components/style/invalidation/element/collector.rs
@@ -71,12 +71,12 @@ impl<'a, 'b: 'a, E: TElement> StateAndAttrInvalidationProcessor<'a, 'b, E> {
         cut_off_inheritance: bool,
         element: E,
         data: &'a mut ElementData,
-        nth_index_cache: Option<&'a mut NthIndexCache>,
+        nth_index_cache: &'a mut NthIndexCache,
     ) -> Self {
         let matching_context = MatchingContext::new_for_visited(
             MatchingMode::Normal,
             None,
-            nth_index_cache,
+            Some(nth_index_cache),
             VisitedHandlingMode::AllLinksVisitedAndUnvisited,
             shared_context.quirks_mode(),
         );
diff --git a/components/style/traversal.rs b/components/style/traversal.rs
index da7750d1ff0..6a99d597d1b 100644
--- a/components/style/traversal.rs
+++ b/components/style/traversal.rs
@@ -10,6 +10,7 @@ use dom::{NodeInfo, OpaqueNode, TElement, TNode};
 use invalidation::element::restyle_hints::RestyleHint;
 use matching::{ChildCascadeRequirement, MatchMethods};
 use selector_parser::PseudoElement;
+use selectors::NthIndexCache;
 use sharing::StyleSharingTarget;
 use smallvec::SmallVec;
 use style_resolver::{PseudoElementResolution, StyleResolverForElement};
@@ -153,11 +154,12 @@ pub trait DomTraversal<E: TElement> : Sync {
             if !traversal_flags.for_animation_only() {
                 // Invalidate our style, and that of our siblings and
                 // descendants as needed.
-                //
-                // FIXME(emilio): an nth-index cache could be worth here, even
-                // if temporary?
-                let invalidation_result =
-                    data.invalidate_style_if_needed(root, shared_context, None, None);
+                let invalidation_result = data.invalidate_style_if_needed(
+                    root,
+                    shared_context,
+                    None,
+                    &mut NthIndexCache::default(),
+                );
 
                 if invalidation_result.has_invalidated_siblings() {
                     let actual_root = root.traversal_parent()
@@ -802,7 +804,7 @@ where
                 child,
                 &context.shared,
                 Some(&context.thread_local.stack_limit_checker),
-                Some(&mut context.thread_local.nth_index_cache)
+                &mut context.thread_local.nth_index_cache,
             );
         }
 
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index 894e66579bb..35ca8d0f2fd 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -6,7 +6,7 @@ use cssparser::{Parser, ParserInput};
 use cssparser::ToCss as ParserToCss;
 use env_logger::LogBuilder;
 use malloc_size_of::MallocSizeOfOps;
-use selectors::Element;
+use selectors::{Element, NthIndexCache};
 use selectors::matching::{MatchingContext, MatchingMode, matches_selector};
 use servo_arc::{Arc, ArcBorrow, RawOffsetArc};
 use std::cell::RefCell;
@@ -4478,15 +4478,13 @@ pub extern "C" fn Servo_ProcessInvalidations(
     let mut data = data.as_mut().map(|d| &mut **d);
 
     if let Some(ref mut data) = data {
-        // FIXME(emilio): an nth-index cache could be worth here, even
-        // if temporary?
-        //
-        // Also, ideally we could share them across all the elements?
+        // FIXME(emilio): Ideally we could share the nth-index-cache across all
+        // the elements?
         let result = data.invalidate_style_if_needed(
             element,
             &shared_style_context,
             None,
-            None,
+            &mut NthIndexCache::default(),
         );
 
         if result.has_invalidated_siblings() {