diff --git a/inform7/Internal/Inter/WorldModelKit/Sections/ListWriter.i6t b/inform7/Internal/Inter/WorldModelKit/Sections/ListWriter.i6t
index 378dd15a5..8c881dc88 100644
--- a/inform7/Internal/Inter/WorldModelKit/Sections/ListWriter.i6t
+++ b/inform7/Internal/Inter/WorldModelKit/Sections/ListWriter.i6t
@@ -450,7 +450,7 @@ objects which in all other circumstances never have children in the tree.
 
 #Ifdef DBLW;
 [ DiagnoseSortList obj memb;
-    for (memb=child(obj): memb~=nothing: memb=sibling(memb)) print memb, " --> "; new_line;
+    for (memb=obj: memb~=nothing: memb=sibling(memb)) print memb, " --> "; new_line;
 ];
 #Endif;