diff --git a/lualib-src/lua-bson.c b/lualib-src/lua-bson.c
index ca73bae0..1799d7bf 100644
--- a/lualib-src/lua-bson.c
+++ b/lualib-src/lua-bson.c
@@ -68,6 +68,13 @@ struct bson_reader {
 	int size;
 };
 
+static inline int32_t
+get_length(const uint8_t * data) {
+	const uint8_t * b = (const uint8_t *)data;
+	int32_t len = b[0] | b[1]<<8 | b[2]<<16 | b[3]<<24;
+	return len;
+}
+
 static inline void
 bson_destroy(struct bson *b) {
 	if (b->ptr != b->buffer) {
@@ -644,7 +651,7 @@ static int
 lmakeindex(lua_State *L) {
 	int32_t *bson = luaL_checkudata(L,1,"bson");
 	const uint8_t * start = (const uint8_t *)bson;
-	struct bson_reader br = { start+4, *bson - 5 };
+	struct bson_reader br = { start+4, get_length(start) - 5 };
 	lua_newtable(L);
 
 	for (;;) {
@@ -820,7 +827,9 @@ ldecode(lua_State *L) {
 	if (data == NULL) {
 		return 0;
 	}
-	struct bson_reader br = { (const uint8_t *)data , *data };
+	const uint8_t * b = (const uint8_t *)data;
+	int32_t len = get_length(b);
+	struct bson_reader br = { b , len };
 
 	unpack_dict(L, &br, false);
 
diff --git a/lualib-src/lua-mongo.c b/lualib-src/lua-mongo.c
index a0d312fd..3e4666dc 100644
--- a/lualib-src/lua-mongo.c
+++ b/lualib-src/lua-mongo.c
@@ -260,6 +260,13 @@ op_reply(lua_State *L) {
 			lua_pushnil(L);
 			lua_rawseti(L, 2, i);
 		}
+	} else {
+		if (sz >= 4) {
+			sz -= get_length((document)doc);
+		}
+	}
+	if (sz != 0) {
+		return luaL_error(L, "Invalid result bson document");
 	}
 	lua_pushboolean(L,1);
 	lua_pushinteger(L, id);
diff --git a/lualib/mongo.lua b/lualib/mongo.lua
index 7b1c6f69..b04f7b46 100644
--- a/lualib/mongo.lua
+++ b/lualib/mongo.lua
@@ -98,7 +98,7 @@ function mongo.client( conf )
 		host = obj.host,
 		port = obj.port,
 		response = dispatch_reply,
-		auth = mongo_auth(conf),
+		auth = mongo_auth(obj),
 	}
 	setmetatable(obj, client_meta)
 	obj.__sock:connect(true)	-- try connect only once