diff --git a/parallel_hashmap/phmap.h b/parallel_hashmap/phmap.h
index 3b7f602..48573b9 100644
--- a/parallel_hashmap/phmap.h
+++ b/parallel_hashmap/phmap.h
@@ -1154,7 +1154,7 @@ public:
 
     raw_hash_set(const raw_hash_set& that, const allocator_type& a)
         : raw_hash_set(0, that.hash_ref(), that.eq_ref(), a) {
-        reserve(that.size());
+        reserve(that.capacity());
         // Because the table is guaranteed to be empty, we can do something faster
         // than a full `insert`.
         for (const auto& v : that) {