diff --git a/app-proto/src/assembly.rs b/app-proto/src/assembly.rs
index b119d5b..9a4dd94 100644
--- a/app-proto/src/assembly.rs
+++ b/app-proto/src/assembly.rs
@@ -23,10 +23,7 @@ pub struct Element {
     
     // the configuration matrix column index that was assigned to this element
     // last time the assembly was realized
-    /* TO DO */
-    // this is public, as a kludge, because `Element` doesn't have a constructor
-    // yet. it should be made private as soon as the constructor is written
-    pub index: usize
+    index: usize
 }
 
 impl Element {