diff --git a/src/list.hpp b/src/list.hpp
index 8dce75f2b84f254382be8a0f26f3f00f9ed22eb2..59782b46a878ea3b89d0bb76e60f13abb99de5bc 100644
--- a/src/list.hpp
+++ b/src/list.hpp
@@ -15,7 +15,7 @@ struct ZigList {
     void deinit() {
         free(items);
     }
-    void append(T item) {
+    void append(const T& item) {
         ensure_capacity(length + 1);
         items[length++] = item;
     }