diff --git a/extmod/modbtree.c b/extmod/modbtree.c
index 8b76885809..a2bff06d44 100644
--- a/extmod/modbtree.c
+++ b/extmod/modbtree.c
@@ -352,7 +352,7 @@ STATIC mp_obj_t mod_btree_open(size_t n_args, const mp_obj_t *pos_args, mp_map_t
     openinfo.psize = args.pagesize.u_int;
     openinfo.minkeypage = args.minkeypage.u_int;
 
-    DB *db = __bt_open(pos_args[0], &btree_stream_fvtable, &openinfo, /*dflags*/0);
+    DB *db = __bt_open(MP_OBJ_TO_PTR(pos_args[0]), &btree_stream_fvtable, &openinfo, /*dflags*/0);
     if (db == NULL) {
         mp_raise_OSError(errno);
     }
diff --git a/py/py.mk b/py/py.mk
index 27565948d5..d6392e9973 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -77,7 +77,7 @@ endif
 
 ifeq ($(MICROPY_PY_BTREE),1)
 BTREE_DIR = lib/berkeley-db-1.xx
-BTREE_DEFS = -D__DBINTERFACE_PRIVATE=1 -Dmpool_error=printf -Dabort=abort_ -Dvirt_fd_t=mp_obj_t "-DVIRT_FD_T_HEADER=<py/obj.h>" $(BTREE_DEFS_EXTRA)
+BTREE_DEFS = -D__DBINTERFACE_PRIVATE=1 -Dmpool_error=printf -Dabort=abort_ "-Dvirt_fd_t=void*" $(BTREE_DEFS_EXTRA)
 INC += -I$(TOP)/$(BTREE_DIR)/PORT/include
 SRC_MOD += extmod/modbtree.c
 SRC_MOD += $(addprefix $(BTREE_DIR)/,\