diff --git a/changelog.md b/changelog.md
index 2ebb2f9ea..fe0417d77 100644
--- a/changelog.md
+++ b/changelog.md
@@ -3,6 +3,7 @@
 ## 2.0.3
 * `CHG` improve memory usage
 * `FIX` some dialog boxes block the initialization process
+* `FIX` diagnostics `undefined-field`: blocks main thread
 * `FIX` [#565](https://github.com/sumneko/lua-language-server/issues/565)
 
 ## 2.0.2
diff --git a/script/core/diagnostics/deprecated.lua b/script/core/diagnostics/deprecated.lua
index 282058455..d6265f645 100644
--- a/script/core/diagnostics/deprecated.lua
+++ b/script/core/diagnostics/deprecated.lua
@@ -35,8 +35,6 @@ return function (uri, callback)
             end
         end
 
-        await.delay()
-
         local id = noder.getID(src)
         if not id then
             return
@@ -46,6 +44,8 @@ return function (uri, callback)
             return
         end
 
+        await.delay()
+
         if not vm.isDeprecated(src, true) then
             cache[id] = true
             return
diff --git a/script/core/diagnostics/undefined-field.lua b/script/core/diagnostics/undefined-field.lua
index fd1fdbd9a..8dad36eb8 100644
--- a/script/core/diagnostics/undefined-field.lua
+++ b/script/core/diagnostics/undefined-field.lua
@@ -3,6 +3,7 @@ local vm      = require 'vm'
 local lang    = require 'language'
 local guide   = require 'parser.guide'
 local noder   = require 'core.noder'
+local await   = require 'await'
 
 local SkipCheckClass = {
     ['unknown'] = true,
@@ -27,6 +28,9 @@ return function (uri, callback)
         if cache[id] then
             return
         end
+
+        await.delay()
+
         if #vm.getDefs(src) > 0 then
             cache[id] = true
             return