diff --git a/src/l52util.c b/src/l52util.c
index 5633f5d..3eb86d8 100644
--- a/src/l52util.c
+++ b/src/l52util.c
@@ -156,3 +156,11 @@ int64_t lutil_optint64(lua_State *L, int idx, int64_t v){
 void lutil_pushnvalues(lua_State *L, int n){
   for(;n;--n) lua_pushvalue(L, -n);
 }
+
+int lutil_is_null(lua_State *L, int i){
+  return lua_islightuserdata(L, i) && 0 == lua_touserdata(L, i);
+}
+
+void lutil_push_null(lua_State *L){
+  lua_pushlightuserdata(L, (void*)0);
+}
diff --git a/src/l52util.h b/src/l52util.h
index 4d6b2fe..14849fe 100644
--- a/src/l52util.h
+++ b/src/l52util.h
@@ -88,4 +88,8 @@ int64_t lutil_optint64(lua_State *L, int idx, int64_t v);
 
 void lutil_pushnvalues(lua_State *L, int n);
 
+int lutil_is_null(lua_State *L, int i);
+
+void lutil_push_null(lua_State *L);
+
 #endif
diff --git a/src/lceasy.c b/src/lceasy.c
index a85dc6b..a5b8685 100644
--- a/src/lceasy.c
+++ b/src/lceasy.c
@@ -344,16 +344,22 @@ static int lcurl_opt_set_off_(lua_State *L, int opt){
 
 static int lcurl_opt_set_string_(lua_State *L, int opt, int store){
   lcurl_easy_t *p = lcurl_geteasy(L);
-  CURLcode code;
+  CURLcode code; const char *value;
 
-  luaL_argcheck(L, lua_type(L, 2) == LUA_TSTRING, 2, "string expected");
+  luaL_argcheck(L, lua_type(L, 2) == LUA_TSTRING || lutil_is_null(L, 2), 2, "string expected");
 
-  code = curl_easy_setopt(p->curl, opt, lua_tostring(L, 2));
+  value = lua_tostring(L, 2);
+  code = curl_easy_setopt(p->curl, opt, value);
   if(code != CURLE_OK){
     return lcurl_fail_ex(L, p->err_mode, LCURL_ERROR_EASY, code);
   }
 
-  if(store)lcurl_storage_preserve_iv(L, p->storage, opt, 2);
+  if(store){
+    if(value)
+      lcurl_storage_preserve_iv(L, p->storage, opt, 2);
+    else
+      lcurl_storage_remove_i(L, p->storage, opt);
+  }
 
   lua_settop(L, 1);
   return 1;
@@ -365,7 +371,7 @@ static int lcurl_opt_set_slist_(lua_State *L, int opt, int list_no){
   CURLcode code;
   int ref = p->lists[list_no];
 
-  luaL_argcheck(L, list || lua_istable(L, 2), 2, "array expected");
+  luaL_argcheck(L, list || lua_istable(L, 2) || lutil_is_null(L, 2), 2, "array expected");
 
   if(ref != LUA_NOREF){
     struct curl_slist *tmp = lcurl_storage_remove_slist(L, p->storage, ref);
diff --git a/src/lcmime.c b/src/lcmime.c
index 06c3550..33e12a9 100644
--- a/src/lcmime.c
+++ b/src/lcmime.c
@@ -135,7 +135,7 @@ int lcurl_mime_set_lua(lua_State *L, lcurl_mime_t *p, lua_State *v){
 
 #define IS_NILORSTR(L, i) (lua_type(L, i) == LUA_TSTRING) || (lua_type(L, i) == LUA_TNIL)
 #define IS_TABLE(L, i) lua_type(L, i) == LUA_TTABLE
-#define IS_FALSE(L, i) (lua_type(L, i) == LUA_TBOOLEAN) && (!lua_toboolean(L, i))
+#define IS_FALSE(L, i) ((lua_type(L, i) == LUA_TBOOLEAN) && (!lua_toboolean(L, i))) || lutil_is_null(L,i)
 #define IS_OPTSTR(L, i) (IS_FALSE(L, i)) || (IS_NILORSTR(L, i))
 
 static int lutil_isarray(lua_State *L, int i){
@@ -512,13 +512,13 @@ static int lcurl_mime_part_headers(lua_State *L){
   }
   else{
     list = lcurl_util_to_slist(L, 2);
-    luaL_argcheck(L, list, 2, "array or nil expected");
+    luaL_argcheck(L, list || IS_TABLE(L, 2), 2, "array or null expected");
   }
 
   ret = curl_mime_headers(p->part, list, 1);
 
   if(ret != CURLE_OK){
-    curl_slist_free_all(list);
+    if(list) curl_slist_free_all(list);
     return lcurl_fail_ex(L, p->err_mode, LCURL_ERROR_EASY, ret);
   }
 
diff --git a/src/lcmulti.c b/src/lcmulti.c
index 4bfc1e7..9485fca 100644
--- a/src/lcmulti.c
+++ b/src/lcmulti.c
@@ -424,16 +424,22 @@ static int lcurl_opt_set_string_array_(lua_State *L, int opt){
   lcurl_multi_t *p = lcurl_getmulti(L);
   CURLMcode code;
   int n;
-  luaL_argcheck(L, lua_type(L, 2) == LUA_TTABLE, 2, "array expected");
-  n = lua_rawlen(L, 2);
+
+  if (lutil_is_null(L, 2)) {
+    n = 0;
+  }
+  else {
+    luaL_argcheck(L, lua_type(L, 2) == LUA_TTABLE, 2, "array expected");
+    n = lua_rawlen(L, 2);
+  }
+
   if(n == 0){
-    char *val[] = {NULL};
-    code = curl_multi_setopt(p->curl, opt, val);
+    code = curl_multi_setopt(p->curl, opt, 0);
   }
   else{
     int i;
-    char const* *val = malloc(sizeof(char*) * (n + 1));
-    if(!*val){
+    char const**val = malloc(sizeof(char*) * (n + 1));
+    if(!val){
       return lcurl_fail_ex(L, p->err_mode, LCURL_ERROR_MULTI, CURLM_OUT_OF_MEMORY);
     }
     for(i = 1; i <= n; ++i){
diff --git a/src/lcoptshare.h b/src/lcoptshare.h
index 298255d..95960bb 100644
--- a/src/lcoptshare.h
+++ b/src/lcoptshare.h
@@ -14,11 +14,14 @@ OPT_ENTRY(unshare,              UNSHARE,                   LNG,     0 )
 FLG_ENTRY( LOCK_DATA_COOKIE                  )
 FLG_ENTRY( LOCK_DATA_DNS                     )
 FLG_ENTRY( LOCK_DATA_SSL_SESSION             )
+FLG_ENTRY( LOCK_DATA_CONNECT                 )
 
 #ifdef OPT_ENTRY_IS_NULL
 #  undef OPT_ENTRY
+#  undef OPT_ENTRY_IS_NULL
 #endif
 
 #ifdef FLG_ENTRY_IS_NULL
 #  undef FLG_ENTRY
+#  undef FLG_ENTRY_IS_NULL
 #endif
diff --git a/src/lcurl.c b/src/lcurl.c
index 41b266d..507b0ee 100644
--- a/src/lcurl.c
+++ b/src/lcurl.c
@@ -270,6 +270,9 @@ static int luaopen_lcurl_(lua_State *L, const struct luaL_Reg *func){
 
   lcurl_util_set_const(L, lcurl_flags);
 
+  lutil_push_null(L);
+  lua_setfield(L, -2, "null");
+
   return 1;
 }
 
diff --git a/src/lcutils.c b/src/lcutils.c
index e4428fb..cbf1865 100644
--- a/src/lcutils.c
+++ b/src/lcutils.c
@@ -171,8 +171,6 @@ int lcurl_set_callback(lua_State *L, lcurl_callback_t *c, int i, const char *met
   luaL_argcheck(L, !lua_isnoneornil(L, i), i, "no function present");
   luaL_argcheck(L, (top < (i + 2)), i + 2, "no arguments expected");
 
-  // if(top > (i + 1)) lua_settop(L, i + 1); // this for force ignore other arguments
-
   assert((top == i)||(top == (i + 1)));
 
   if(c->ud_ref != LUA_NOREF){
@@ -185,6 +183,19 @@ int lcurl_set_callback(lua_State *L, lcurl_callback_t *c, int i, const char *met
     c->cb_ref = LUA_NOREF;
   }
 
+  if(lutil_is_null(L, i)){
+    if(top == (i + 1)){
+      // Do we can just ignore this?
+      luaL_argcheck(L, 
+        lua_isnoneornil(L, i + 1) || lutil_is_null(L, i + 1)
+        ,i + 1, "no context allowed when set callback to null"
+      );
+    }
+    lua_pop(L, top - i + 1);
+
+    return 1;
+  }
+
   if(lua_gettop(L) == (i + 1)){// function + context
     c->ud_ref = luaL_ref(L, LCURL_LUA_REGISTRY);
     c->cb_ref = luaL_ref(L, LCURL_LUA_REGISTRY);
diff --git a/test/test_easy.lua b/test/test_easy.lua
index baef535..be9e08f 100644
--- a/test/test_easy.lua
+++ b/test/test_easy.lua
@@ -35,6 +35,8 @@ local POST_URL = "http://127.0.0.1:7090/post"
 local weak_ptr, gc_collect, is_curl_ge, read_file, stream, Stream, dump_request =
   utils.import('weak_ptr', 'gc_collect', 'is_curl_ge', 'read_file', 'stream', 'Stream', 'dump_request')
 
+local null = curl.null
+
 local ENABLE = true
 
 local _ENV = TEST_CASE'curl error'           if ENABLE then
@@ -151,9 +153,16 @@ function test_reset_write_callback()
   assert_equal(c, c:setopt_writefunction(f))
   assert_equal(c, c:setopt_writefunction(f.write, f))
   assert_equal(c, c:setopt_writefunction(print))
+  assert_equal(c, c:setopt_writefunction(print, null))
+  assert_equal(c, c:setopt_writefunction(null))
+  assert_equal(c, c:setopt_writefunction(null, nil))
+  assert_equal(c, c:setopt_writefunction(null, null))
   assert_error(function()c:setopt_writefunction()end)
   assert_error(function()c:setopt_writefunction(nil)end)
   assert_error(function()c:setopt_writefunction(nil, f)end)
+  assert_error(function()c:setopt_writefunction(null, {})end)
+  assert_error(function()c:setopt_writefunction(print, {}, nil)end)
+  assert_error(function()c:setopt_writefunction(print, {}, null)end)
 end
 
 function test_write_pass_01()
@@ -208,6 +217,38 @@ function test_write_coro()
   assert_equal(co2, called)
 end
 
+function test_write_pass_null_context()
+  c = assert(curl.easy{
+    url = GET_URL;
+  })
+
+  local context
+  assert_equal(c, c:setopt_writefunction(function(ctx)
+    context = ctx
+    return true
+  end, null))
+
+  assert_equal(c, c:perform())
+  assert_equal(null, context)
+end
+
+function test_write_pass_nil_context()
+  c = assert(curl.easy{
+    url = GET_URL;
+  })
+
+  local context, called
+  assert_equal(c, c:setopt_writefunction(function(ctx)
+    context = ctx
+    called = true
+    return true
+  end, nil))
+
+  assert_equal(c, c:perform())
+  assert_true(called)
+  assert_nil(context)
+end
+
 end
 
 local _ENV = TEST_CASE'progress_callback'    if ENABLE then
@@ -379,9 +420,14 @@ function test_reset_header_callback()
   assert_equal(c, c:setopt_headerfunction(f))
   assert_equal(c, c:setopt_headerfunction(f.header, f))
   assert_equal(c, c:setopt_headerfunction(print))
+  assert_equal(c, c:setopt_headerfunction(null))
+  assert_equal(c, c:setopt_headerfunction(null, nil))
+  assert_equal(c, c:setopt_headerfunction(null, null))
   assert_error(function()c:setopt_headerfunction()end)
   assert_error(function()c:setopt_headerfunction(nil)end)
   assert_error(function()c:setopt_headerfunction(nil, f)end)
+  assert_error(function()c:setopt_headerfunction(null, {})end)
+  assert_error(function()c:setopt_headerfunction(print, {}, nil)end)
 end
 
 function test_header_pass_01()
@@ -1060,4 +1106,62 @@ end
 
 end
 
+local _ENV = TEST_CASE'set_null'             if ENABLE then
+
+local c, m
+
+function teardown()
+  if c then c:close() end
+  if m then m:close() end
+  m, c = nil
+end
+
+function test_string()
+  c = curl.easy()
+  c:setopt_accept_encoding('gzip')
+  local body, headers = assert_string(dump_request(c))
+  assert_match("Accept%-Encoding:%s*gzip", headers)
+
+  c:setopt_accept_encoding(null)
+  body, headers = assert_string(dump_request(c))
+  assert_not_match("Accept%-Encoding:%s*gzip", headers)
+end
+
+function test_string_via_table()
+  c = curl.easy()
+  c:setopt_accept_encoding('gzip')
+  local body, headers = assert_string(dump_request(c))
+  assert_match("Accept%-Encoding:%s*gzip", headers)
+
+  c:setopt{ accept_encoding = null }
+  body, headers = assert_string(dump_request(c))
+  assert_not_match("Accept%-Encoding:%s*gzip", headers)
+end
+
+function test_slist()
+  c = curl.easy()
+  c:setopt_httpheader({'X-Custom: value'})
+  c:setopt_httpheader(null)
+  local body, headers = assert_string(dump_request(c))
+  assert_not_match("X%-Custom:%s*value\r\n", headers)
+end
+
+function test_slist_via_table()
+  c = curl.easy()
+  c:setopt_httpheader({'X-Custom: value'})
+  c:setopt{httpheader = null}
+  local body, headers = assert_string(dump_request(c))
+  assert_not_match("X%-Custom:%s*value\r\n", headers)
+end
+
+function test_multi_set_array()
+  m = curl.multi()
+  m:setopt_pipelining_site_bl{
+    '127.0.0.1'
+  }
+  assert_equal(m, m:setopt_pipelining_site_bl(null))
+end
+
+end
+
 RUN()
diff --git a/test/test_mime.lua b/test/test_mime.lua
index e7239f4..762d896 100644
--- a/test/test_mime.lua
+++ b/test/test_mime.lua
@@ -19,6 +19,8 @@ local weak_ptr, gc_collect, dump_mime_ = utils.import('weak_ptr', 'gc_collect',
 
 local GET_URL = 'http://127.0.0.1:7090/get'
 
+local null = curl.null
+
 local function is_freed(c)
   return not not string.find(tostring(c), '%(freed%)')
 end
@@ -313,6 +315,15 @@ function test_unset_name()
   assert_not_match('Content%-Disposition:.-name="test"', info)
 end
 
+function test_unset_name_by_null()
+  mime:addpart():data('hello', 'test/html', 'test'):name(null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_match('Content%-Type:%s+test/html', info)
+  assert_not_match('Content%-Disposition:.-name="test"', info)
+end
+
 function test_unset_type()
   mime:addpart():data('hello', 'test/html'):type(false)
 
@@ -321,6 +332,14 @@ function test_unset_type()
   assert_not_match('Content%-Type:%s+test/html', info)
 end
 
+function test_unset_type_by_null()
+  mime:addpart():data('hello', 'test/html'):type(null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_not_match('Content%-Type:%s+test/html', info)
+end
+
 function test_unset_headers()
   mime:addpart():data('hello', 'test/html',{
     'X-Custom-Header: hello'
@@ -331,6 +350,26 @@ function test_unset_headers()
   assert_not_match('X%-Custom%-Header:%s*hello', info)
 end
 
+function test_unset_headers_by_null()
+  mime:addpart():data('hello', 'test/html',{
+    'X-Custom-Header: hello'
+  }):headers(null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_not_match('X%-Custom%-Header:%s*hello', info)
+end
+
+function test_unset_headers_by_empty_array()
+  mime:addpart():data('hello', 'test/html',{
+    'X-Custom-Header: hello'
+  }):headers({})
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_not_match('X%-Custom%-Header:%s*hello', info)
+end
+
 function test_unset_data()
   mime:addpart():data('hello', 'test/html', 'test'):data(false)
 
@@ -340,6 +379,15 @@ function test_unset_data()
   assert_match('Content%-Disposition:.-name="test"', info)
 end
 
+function test_unset_data_by_null()
+  mime:addpart():data('hello', 'test/html', 'test'):data(null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_not_match('\r\n\r\nhello', info)
+  assert_match('Content%-Type:%s+test/html', info)
+  assert_match('Content%-Disposition:.-name="test"', info)
+end
+
 function test_unset_data_type_1()
   local part = mime:addpart():data('hello', 'test/html', 'test', {
     'X-Custom-Header: hello'
@@ -352,6 +400,18 @@ function test_unset_data_type_1()
   assert_match('X%-Custom%-Header:%s*hello', info)
 end
 
+function test_unset_data_type_1_by_null()
+  local part = mime:addpart():data('hello', 'test/html', 'test', {
+    'X-Custom-Header: hello'
+  }):data('hello', null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_not_match('Content%-Type:%s+test/html', info)
+  assert_match('Content%-Disposition:.-name="test"', info)
+  assert_match('X%-Custom%-Header:%s*hello', info)
+end
+
 function test_unset_data_type_2()
   local part = mime:addpart():data('hello', 'test/html', 'test', {
     'X-Custom-Header: hello'
@@ -376,6 +436,18 @@ function test_unset_data_name_1()
   assert_match('X%-Custom%-Header:%s*hello', info)
 end
 
+function test_unset_data_name_1_by_null()
+  local part = mime:addpart():data('hello', 'test/html', 'test', {
+    'X-Custom-Header: hello'
+  }):data('hello', nil, null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_match('Content%-Type:%s+test/html', info)
+  assert_not_match('Content%-Disposition:.-name="test"', info)
+  assert_match('X%-Custom%-Header:%s*hello', info)
+end
+
 function test_unset_data_name_2()
   local part = mime:addpart():data('hello', 'test/html', 'test', {
     'X-Custom-Header: hello'
@@ -400,6 +472,18 @@ function test_unset_data_header()
   assert_not_match('X%-Custom%-Header:%s*hello', info)
 end
 
+function test_unset_data_header_by_null()
+  local part = mime:addpart():data('hello', 'test/html', 'test', {
+    'X-Custom-Header: hello'
+  }):data('hello', nil, nil, nil, null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_match('Content%-Type:%s+test/html', info)
+  assert_match('Content%-Disposition:.-name="test"', info)
+  assert_not_match('X%-Custom%-Header:%s*hello', info)
+end
+
 function test_unset_data_filename_1()
   local part = mime:addpart():data('hello', 'test/html', 'test', 'test.html', {
     'X-Custom-Header: hello'
@@ -409,7 +493,20 @@ function test_unset_data_filename_1()
   assert_match('\r\n\r\nhello', info)
   assert_match('Content%-Type:%s+test/html', info)
   assert_match('Content%-Disposition:.-%sname="test"', info)
-  assert_not_match('Content%-Disposition:.-%sname="test%.html"', info)
+  assert_not_match('Content%-Disposition:.-%sfilename="test%.html"', info)
+  assert_match('X%-Custom%-Header:%s*hello', info)
+end
+
+function test_unset_data_filename_1_by_null()
+  local part = mime:addpart():data('hello', 'test/html', 'test', 'test.html', {
+    'X-Custom-Header: hello'
+  }):data('hello', nil, nil, null)
+
+  local info = assert_string(dump_mime(mime))
+  assert_match('\r\n\r\nhello', info)
+  assert_match('Content%-Type:%s+test/html', info)
+  assert_match('Content%-Disposition:.-%sname="test"', info)
+  assert_not_match('Content%-Disposition:.-%sfilename="test%.html"', info)
   assert_match('X%-Custom%-Header:%s*hello', info)
 end