diff --git a/src/blocks/scratch3_data.js b/src/blocks/scratch3_data.js
index 78191c5d..74987408 100644
--- a/src/blocks/scratch3_data.js
+++ b/src/blocks/scratch3_data.js
@@ -180,7 +180,7 @@ class Scratch3DataBlocks {
         if (index === Cast.LIST_INVALID) {
             return;
         }
-        list.value.splice(index - 1, 1, item);
+        list.value[index - 1] = item;
         list._monitorUpToDate = false;
     }