diff --git a/Assets/Fungus/Docs/CHANGELOG.txt b/Assets/Fungus/Docs/CHANGELOG.txt
index e95a639e..e56d654e 100644
--- a/Assets/Fungus/Docs/CHANGELOG.txt
+++ b/Assets/Fungus/Docs/CHANGELOG.txt
@@ -1,6 +1,38 @@
 Changelog {#changelog}
 =========
-[TOC]
+
+v3.12.0 rc1
+======
+
+## Added
+
+- Search should search commands, not just block names (#775). Thanks to AcademyOfF
+- Debug additions (#777) righclicking context menus additions and improvements on commands, blocks, and variables
+- BlockCallers can be seen within the block inspector
+- Variable referencers can be seen logged to the console
+- Added a custom script importer for lua files. Thanks to Matthew Barnes
+- Added Asmdefs
+- Fungus Editor Prefs button to locate FungusEditorResources and changelog
+
+## Fixed
+
+- Defines and fallbacks for 2017 and 2018 (#781)
+- CommandListAdapter sync command selection bidirectionally with selection in underlying reorderablelist
+- Command text with 'Error:' shows red
+- HighSpeedWriterFix; corrected rate of characters and more than 1 character per frame issue.
+- FilterBlocks during SceneChange, now refresh as expected
+- Command and Variables outside of Fungus assembly now locate
+- Character selection preventing edits bug
+- Restore Edit Mode Tests
+
+## Changed
+
+- FungusManager.cs Use "double checked locking" algorithm to implement the singleton for "FungusManager" class, which can improve performance. Thanks to AndyHan1001 
+- CommandSearchHeightFallback on some versions of Unity editor inspector height is not returning correctly so we make an educated guess if it seems unreliable
+- More elaborated use of text in TMPro demo
+- Block Inspector forces type at creation. Thanks to Michaelwolf95
+- Warning when requesting menu elements that are not avaialble, such as more menu items that you have created.
+
 
 v3.11.5 {#v3.11.5}
 ======
diff --git a/Assets/Fungus/Scripts/Components/FungusManager.cs b/Assets/Fungus/Scripts/Components/FungusManager.cs
index 45ebf836..7076d4eb 100644
--- a/Assets/Fungus/Scripts/Components/FungusManager.cs
+++ b/Assets/Fungus/Scripts/Components/FungusManager.cs
@@ -19,9 +19,9 @@ namespace Fungus
     #endif
     public sealed class FungusManager : MonoBehaviour
     {
-        static FungusManager instance;
+        volatile static FungusManager instance;  // The keyword "volatile" is friendly to the multi-thread.
         static bool applicationIsQuitting = false;
-        static object _lock = new object();
+        readonly static object _lock = new object();  // The keyword "readonly" is friendly to the multi-thread.
 
         void Awake()
         {
@@ -96,18 +96,23 @@ namespace Fungus
                     return null;
                 }
 
-                lock (_lock)
+                // Use "double checked locking" algorithm to implement the singleton for this "FungusManager" class, which can improve performance.
+                if (instance == null)
                 {
-                    if (instance == null)
+                    lock (_lock)
                     {
-                        var go = new GameObject();
-                        go.name = "FungusManager";
-                        DontDestroyOnLoad(go);
-                        instance = go.AddComponent<FungusManager>();
-                    }
+                        if (instance == null)
+                        {
+                            var go = new GameObject();
+                            go.name = "FungusManager";
+                            DontDestroyOnLoad(go);
+                            instance = go.AddComponent<FungusManager>();
+                        }
 
-                    return instance;
+                    }
                 }
+                
+                return instance;
             }
         }