diff --git a/lemon/maps.h b/lemon/maps.h
--- a/lemon/maps.h
+++ b/lemon/maps.h
@@ -3252,7 +3252,7 @@
 
     virtual void add(const Key& key) {
       Parent::add(key);
-      unlace(key);
+      lace(key);
     }
 
     virtual void add(const std::vector<Key>& keys) {
diff --git a/test/maps_test.cc b/test/maps_test.cc
--- a/test/maps_test.cc
+++ b/test/maps_test.cc
@@ -641,6 +641,7 @@
 
     const int num = 10;
     Graph g;
+    Ibm map0(g, true);
     std::vector<Item> items;
     for (int i = 0; i < num; ++i) {
       items.push_back(g.addNode());
@@ -722,6 +723,7 @@
 
     const int num = 10;
     Graph g;
+    Iim map0(g, 0);
     std::vector<Item> items;
     for (int i = 0; i < num; ++i) {
       items.push_back(g.addNode());
@@ -772,6 +774,7 @@
 
     const int num = 10;
     Graph g;
+    Ivm map0(g, 0.0);
     std::vector<Item> items;
     for (int i = 0; i < num; ++i) {
       items.push_back(g.addNode());