diff --git a/m-bptree.h b/m-bptree.h
index 7a68f896..c89c061f 100644
--- a/m-bptree.h
+++ b/m-bptree.h
@@ -36,10 +36,10 @@
 
 /* Define a B+tree of a given type, of size N.
    USAGE: BPTREE_DEF(name, N, type, [, oplist_of_the_type]) */
-#define BPTREE_DEF(name, N, type, oplist)                               \
-  BPTREEI_DEF2(name, N, type, oplist, type, oplist, 0,                  \
-               M_C(name, _t), M_C(name, _node_t), M_C(name, _pit_t),    \
-               M_C(name, _it_t))
+#define BPTREE_DEF(name, N, ...)					\
+  BPTREEI_DEF(M_IF_NARGS_EQ1(__VA_ARGS__)				\
+  ((name, N, __VA_ARGS__, M_GLOBAL_OPLIST_OR_DEF(__VA_ARGS__), __VA_ARGS__, M_GLOBAL_OPLIST_OR_DEF(__VA_ARGS__), 0, M_C(name, _t), M_C(name, _node_t), M_C(name, _pit_t), M_C(name, _it_t) ), \
+   (name, N, __VA_ARGS__,                                    __VA_ARGS__,                                       0, M_C(name, _t), M_C(name, _node_t), M_C(name, _pit_t), M_C(name, _it_t) )))
 
 //TODO: oplist
 
@@ -80,6 +80,9 @@
 /* Max depth of any B+tree */
 #define BPTREEI_MAX_STACK ((int)(CHAR_BIT*sizeof (size_t)))
 
+// Deferred evaluation.
+#define BPTREEI_DEF(arg) BPTREEI_DEF2 arg
+
 #define BPTREEI_DEF2(name, N, key_t, key_oplist, value_t, value_oplist, isMap, tree_t, node_t, pit_t, it_t) \
                                                                         \
   M_IF(isMap)(                                                          \
diff --git a/tests/test-mbptree.c b/tests/test-mbptree.c
index d08de26e..77b61977 100644
--- a/tests/test-mbptree.c
+++ b/tests/test-mbptree.c
@@ -31,7 +31,8 @@ BPTREE_DEF2(btree, 3, int, M_DEFAULT_OPLIST, int, M_DEFAULT_OPLIST)
 END_COVERAGE
 BPTREE_DEF2(btree_my, 3, my_mpz_t, MYMPZ2_OPLIST, my_mpz_t, MYMPZ2_OPLIST)
   
-BPTREE_DEF(btree_myset, 3, my_mpz_t, MYMPZ2_OPLIST)
+BPTREE_DEF(btree_intset, 13, int)
+BPTREE_DEF(btree_myset, 15, my_mpz_t, MYMPZ2_OPLIST)
 
 static void test1(void)
 {