diff --git a/tests/test-mbptree.c b/tests/test-mbptree.c
index 55c1f1cc..87fa3cef 100644
--- a/tests/test-mbptree.c
+++ b/tests/test-mbptree.c
@@ -204,10 +204,12 @@ static void test4(void)
     btree_set_at(b1, i, 1000*i);
   assert(btree_size(b1) == 1000);
   btree_init_set(b2, b1);
-  assert(btree_size(b2) == 1000);
+  assert (btree_size(b2) == 1000);
+  assert (btree_equal_p(b1, b2));
   for(int i = 0; i < 1000; i++) {
     bool r = btree_remove(b2, i);
     assert (r == true);
+    assert (!btree_equal_p(b1, b2));
   }
   assert(btree_size(b2) == 0);
 
@@ -216,6 +218,7 @@ static void test4(void)
   assert(btree_size(b2) == 5000);
   btree_set(b2, b1);
   assert(btree_size(b2) == 1000);
+  assert (btree_equal_p(b1, b2));
   for(int i = 0; i < 1000; i++) {
     bool r = btree_remove(b2, i);
     assert (r == true);
@@ -224,6 +227,7 @@ static void test4(void)
 
   btree_set(b1, b2);
   assert(btree_size(b1) == 0);
+  assert (btree_equal_p(b1, b2));
 
   btree_clear(b1);
   btree_clear(b2);