diff --git a/src/luasocket/buffer.c b/src/luasocket/buffer.c
index 5ea97a9..e1ae981 100644
--- a/src/luasocket/buffer.c
+++ b/src/luasocket/buffer.c
@@ -107,10 +107,16 @@ int buffer_meth_send(lua_State *L, p_buffer buf) {
 * object:receive() interface
 \*-------------------------------------------------------------------------*/
 int buffer_meth_receive(lua_State *L, p_buffer buf) {
-    int err = IO_DONE, top = lua_gettop(L);
     luaL_Buffer b;
     size_t size;
-    const char *part = luaL_optlstring(L, 3, "", &size);
+    const char *part;
+    int err = IO_DONE;
+    int top = lua_gettop(L);
+    if (top < 3) {
+        lua_settop(L, 3);
+        top = 3;
+    }
+    part = luaL_optlstring(L, 3, "", &size);
 #ifdef LUASOCKET_DEBUG
     p_timeout tm = timeout_markstart(buf->tm);
 #endif