diff --git a/node.ml b/node.ml
index b9602a5..138fc8d 100644
--- a/node.ml
+++ b/node.ml
@@ -73,11 +73,15 @@ let bind (filter, node) =
   if filter.label = ""
   then (ignore (Log.warn "Binding to empty name forbidden" []); return false)
   else
-    (filter.binding <- Some node;
-     directory := NameSet.add filter !directory;
-     node.names <- StringSet.add filter.label node.names;
-     ignore (Log.info "Node bound" [Sexp.Str filter.label; Sexp.Str node.class_name]);
-     return true)
+    match filter.binding with
+      | None ->
+	filter.binding <- Some node;
+	directory := NameSet.add filter !directory;
+	node.names <- StringSet.add filter.label node.names;
+	ignore (Log.info "Node bound" [Sexp.Str filter.label; Sexp.Str node.class_name]);
+	return true
+      | Some _ ->
+	return false
 
 (* For use in factory constructor functions, hence the odd return type and values *)
 let make_named class_name node_name handler =