diff --git a/components/style/stylesheets/mod.rs b/components/style/stylesheets/mod.rs
index c5d2ec8b8e8..5230ab63e94 100644
--- a/components/style/stylesheets/mod.rs
+++ b/components/style/stylesheets/mod.rs
@@ -556,8 +556,9 @@ impl DeepCloneWithLock for CssRule {
                 ))
             },
             CssRule::Property(ref arc) => {
-                let rule = arc.read_with(guard);
-                CssRule::Property(Arc::new(lock.wrap(rule.clone())))
+                // @property rules are immutable, so we don't need any of the `Locked`
+                // shenanigans, actually, and can just share the rule.
+                CssRule::Property(arc.clone())
             },
             CssRule::Document(ref arc) => {
                 let rule = arc.read_with(guard);