diff --git a/source/funkin/data/DataError.hx b/source/funkin/data/DataError.hx
index 87c99fff5..82f8d9aaf 100644
--- a/source/funkin/data/DataError.hx
+++ b/source/funkin/data/DataError.hx
@@ -4,6 +4,7 @@ import json2object.Position;
 import json2object.Position.Line;
 import json2object.Error;
 
+@:nullSafety
 class DataError
 {
   public static function printError(error:Error):Void
diff --git a/source/funkin/data/DataWrite.hx b/source/funkin/data/DataWrite.hx
index e277cb01c..e7be178b7 100644
--- a/source/funkin/data/DataWrite.hx
+++ b/source/funkin/data/DataWrite.hx
@@ -12,6 +12,7 @@ import haxe.ds.Either;
  *
  * NOTE: Result must include quotation marks if the value is a string! json2object will not add them for you!
  */
+@:nullSafety
 class DataWrite
 {
   /**
diff --git a/source/funkin/data/dialogue/conversation/ConversationRegistry.hx b/source/funkin/data/dialogue/conversation/ConversationRegistry.hx
index 2f79cf973..8eb280046 100644
--- a/source/funkin/data/dialogue/conversation/ConversationRegistry.hx
+++ b/source/funkin/data/dialogue/conversation/ConversationRegistry.hx
@@ -5,6 +5,7 @@ import funkin.play.cutscene.dialogue.ScriptedConversation;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class ConversationRegistry extends BaseRegistry<Conversation, ConversationData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/data/dialogue/dialoguebox/DialogueBoxRegistry.hx b/source/funkin/data/dialogue/dialoguebox/DialogueBoxRegistry.hx
index 681f8566f..ab2474e99 100644
--- a/source/funkin/data/dialogue/dialoguebox/DialogueBoxRegistry.hx
+++ b/source/funkin/data/dialogue/dialoguebox/DialogueBoxRegistry.hx
@@ -6,6 +6,7 @@ import funkin.play.cutscene.dialogue.ScriptedDialogueBox;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class DialogueBoxRegistry extends BaseRegistry<DialogueBox, DialogueBoxData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/data/dialogue/speaker/SpeakerRegistry.hx b/source/funkin/data/dialogue/speaker/SpeakerRegistry.hx
index 96e85aca2..d7263406a 100644
--- a/source/funkin/data/dialogue/speaker/SpeakerRegistry.hx
+++ b/source/funkin/data/dialogue/speaker/SpeakerRegistry.hx
@@ -5,6 +5,7 @@ import funkin.play.cutscene.dialogue.ScriptedSpeaker;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class SpeakerRegistry extends BaseRegistry<Speaker, SpeakerData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/data/freeplay/album/AlbumRegistry.hx b/source/funkin/data/freeplay/album/AlbumRegistry.hx
index a7c3d3990..64b8f8dbd 100644
--- a/source/funkin/data/freeplay/album/AlbumRegistry.hx
+++ b/source/funkin/data/freeplay/album/AlbumRegistry.hx
@@ -6,6 +6,7 @@ import funkin.ui.freeplay.ScriptedAlbum;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class AlbumRegistry extends BaseRegistry<Album, AlbumData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/data/freeplay/player/PlayerRegistry.hx b/source/funkin/data/freeplay/player/PlayerRegistry.hx
index 7d6c6df94..b87bfe11b 100644
--- a/source/funkin/data/freeplay/player/PlayerRegistry.hx
+++ b/source/funkin/data/freeplay/player/PlayerRegistry.hx
@@ -7,6 +7,7 @@ import funkin.save.Save;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class PlayerRegistry extends BaseRegistry<PlayableCharacter, PlayerData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/data/freeplay/style/FreeplayStyleRegistry.hx b/source/funkin/data/freeplay/style/FreeplayStyleRegistry.hx
index f6d75a86a..4142f7321 100644
--- a/source/funkin/data/freeplay/style/FreeplayStyleRegistry.hx
+++ b/source/funkin/data/freeplay/style/FreeplayStyleRegistry.hx
@@ -6,6 +6,7 @@ import funkin.ui.freeplay.ScriptedFreeplayStyle;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class FreeplayStyleRegistry extends BaseRegistry<FreeplayStyle, FreeplayStyleData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/data/stage/StageRegistry.hx b/source/funkin/data/stage/StageRegistry.hx
index 0398222d8..5092756ef 100644
--- a/source/funkin/data/stage/StageRegistry.hx
+++ b/source/funkin/data/stage/StageRegistry.hx
@@ -5,6 +5,7 @@ import funkin.play.stage.ScriptedStage;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class StageRegistry extends BaseRegistry<Stage, StageData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/data/story/level/LevelRegistry.hx b/source/funkin/data/story/level/LevelRegistry.hx
index 4e4f66019..a01fc04a7 100644
--- a/source/funkin/data/story/level/LevelRegistry.hx
+++ b/source/funkin/data/story/level/LevelRegistry.hx
@@ -6,6 +6,7 @@ import funkin.ui.story.ScriptedLevel;
 import funkin.util.tools.ISingleton;
 import funkin.data.DefaultRegistryImpl;
 
+@:nullSafety
 class LevelRegistry extends BaseRegistry<Level, LevelData> implements ISingleton implements DefaultRegistryImpl
 {
   /**
diff --git a/source/funkin/input/TurboActionHandler.hx b/source/funkin/input/TurboActionHandler.hx
index 9425db8cd..16f258f8d 100644
--- a/source/funkin/input/TurboActionHandler.hx
+++ b/source/funkin/input/TurboActionHandler.hx
@@ -13,6 +13,7 @@ import funkin.input.Controls.Action;
  *
  * Example: Pressing Ctrl+Z will undo, while holding Ctrl+Z will start to undo repeatedly.
  */
+@:nullSafety
 class TurboActionHandler extends FlxBasic
 {
   /**
diff --git a/source/funkin/input/TurboButtonHandler.hx b/source/funkin/input/TurboButtonHandler.hx
index 63c2a294b..0e569cde1 100644
--- a/source/funkin/input/TurboButtonHandler.hx
+++ b/source/funkin/input/TurboButtonHandler.hx
@@ -12,6 +12,7 @@ import flixel.FlxBasic;
  *
  * Example: Pressing Ctrl+Z will undo, while holding Ctrl+Z will start to undo repeatedly.
  */
+@:nullSafety
 class TurboButtonHandler extends FlxBasic
 {
   /**
diff --git a/source/funkin/input/TurboKeyHandler.hx b/source/funkin/input/TurboKeyHandler.hx
index 36b8e2087..9495b5802 100644
--- a/source/funkin/input/TurboKeyHandler.hx
+++ b/source/funkin/input/TurboKeyHandler.hx
@@ -11,6 +11,7 @@ import flixel.FlxBasic;
  *
  * Example: Pressing Ctrl+Z will undo, while holding Ctrl+Z will start to undo repeatedly.
  */
+@:nullSafety
 class TurboKeyHandler extends FlxBasic
 {
   /**
diff --git a/source/funkin/modding/PolymodErrorHandler.hx b/source/funkin/modding/PolymodErrorHandler.hx
index dc387900b..63c705f61 100644
--- a/source/funkin/modding/PolymodErrorHandler.hx
+++ b/source/funkin/modding/PolymodErrorHandler.hx
@@ -2,6 +2,7 @@ package funkin.modding;
 
 import polymod.Polymod;
 
+@:nullSafety
 class PolymodErrorHandler
 {
   /**
@@ -47,7 +48,7 @@ class PolymodErrorHandler
         logError(error.message);
 
         // Last word is the class name.
-        var className:String = error.message.split(' ').pop();
+        var className:Null<String> = error.message.split(' ').pop();
         var msg:String = 'Import error in ${error.origin}';
         msg += '\nCould not import unknown class ${className}';
         msg += '\nCheck to ensure the class exists and is spelled correctly.';
diff --git a/source/funkin/modding/PolymodHandler.hx b/source/funkin/modding/PolymodHandler.hx
index d6a548e0b..91dc4adcd 100644
--- a/source/funkin/modding/PolymodHandler.hx
+++ b/source/funkin/modding/PolymodHandler.hx
@@ -25,6 +25,7 @@ import polymod.Polymod;
 /**
  * A class for interacting with Polymod, the atomic modding framework for Haxe.
  */
+@:nullSafety
 class PolymodHandler
 {
   /**
diff --git a/source/funkin/modding/base/Object.hx b/source/funkin/modding/base/Object.hx
index 1484f9882..5337f311f 100644
--- a/source/funkin/modding/base/Object.hx
+++ b/source/funkin/modding/base/Object.hx
@@ -3,11 +3,13 @@ package funkin.modding.base;
 /**
  * An empty base class meant to be extended by scripts.
  */
-
-class Object {
+@:nullSafety
+class Object
+{
   public function new() {}
 
-  public function toString():String {
+  public function toString():String
+  {
     return "(Object)";
   }
 }
diff --git a/source/funkin/modding/events/ScriptEvent.hx b/source/funkin/modding/events/ScriptEvent.hx
index 6710e4138..153795bf1 100644
--- a/source/funkin/modding/events/ScriptEvent.hx
+++ b/source/funkin/modding/events/ScriptEvent.hx
@@ -15,6 +15,7 @@ import openfl.events.KeyboardEvent;
  * This is a base class for all events that are issued to scripted classes.
  * It can be used to identify the type of event called, store data, and cancel event propagation.
  */
+@:nullSafety
 class ScriptEvent
 {
   /**
@@ -255,7 +256,8 @@ class HoldNoteScriptEvent extends NoteScriptEvent
    */
   public var doesNotesplash:Bool = false;
 
-  public function new(type:ScriptEventType, holdNote:SustainTrail, healthChange:Float, score:Int, isComboBreak:Bool, comboCount:Int = 0, cancelable:Bool = false):Void
+  public function new(type:ScriptEventType, holdNote:SustainTrail, healthChange:Float, score:Int, isComboBreak:Bool, comboCount:Int = 0,
+      cancelable:Bool = false):Void
   {
     super(type, null, healthChange, comboCount, true);
     this.holdNote = holdNote;
diff --git a/source/funkin/modding/events/ScriptEventDispatcher.hx b/source/funkin/modding/events/ScriptEventDispatcher.hx
index 7d6e3992f..4333da59d 100644
--- a/source/funkin/modding/events/ScriptEventDispatcher.hx
+++ b/source/funkin/modding/events/ScriptEventDispatcher.hx
@@ -6,6 +6,7 @@ import funkin.modding.IScriptedClass;
 /**
  * Utility functions to assist with handling scripted classes.
  */
+@:nullSafety
 class ScriptEventDispatcher
 {
   /**
diff --git a/source/funkin/modding/events/ScriptEventType.hx b/source/funkin/modding/events/ScriptEventType.hx
index 02de0dc1a..b8f93d086 100644
--- a/source/funkin/modding/events/ScriptEventType.hx
+++ b/source/funkin/modding/events/ScriptEventType.hx
@@ -1,5 +1,6 @@
 package funkin.modding.events;
 
+@:nullSafety
 enum abstract ScriptEventType(String) from String to String
 {
   /**
diff --git a/source/funkin/modding/module/Module.hx b/source/funkin/modding/module/Module.hx
index 2638b82e2..c04084f87 100644
--- a/source/funkin/modding/module/Module.hx
+++ b/source/funkin/modding/module/Module.hx
@@ -8,6 +8,7 @@ import funkin.modding.events.ScriptEvent;
  * A module is a scripted class which receives all events without requiring a specific context.
  * You may have the module active at all times, or only when another script enables it.
  */
+@:nullSafety
 class Module implements IPlayStateScriptedClass implements IStateChangingScriptedClass
 {
   /**
@@ -28,7 +29,7 @@ class Module implements IPlayStateScriptedClass implements IStateChangingScripte
    *
    * Priority 1 is processed before Priority 1000, etc.
    */
-  public var priority(default, set):Int;
+  public var priority(default, set):Int = 1000;
 
   function set_priority(value:Int):Int
   {
diff --git a/source/funkin/modding/module/ModuleHandler.hx b/source/funkin/modding/module/ModuleHandler.hx
index 6c60b0f8c..e4e0ab7d3 100644
--- a/source/funkin/modding/module/ModuleHandler.hx
+++ b/source/funkin/modding/module/ModuleHandler.hx
@@ -10,6 +10,7 @@ import funkin.modding.module.ScriptedModule;
 /**
  * Utility functions for loading and manipulating active modules.
  */
+@:nullSafety
 class ModuleHandler
 {
   static final moduleCache:Map<String, Module> = new Map<String, Module>();
@@ -74,11 +75,15 @@ class ModuleHandler
    * Given two module IDs, sort them by priority.
    * @return 1 or -1 depending on which module has a higher priority.
    */
-  static function sortByPriority(a:String, b:String)
+  static function sortByPriority(a:String, b:String):Int
   {
-    var aModule:Module = moduleCache.get(a);
-    var bModule:Module = moduleCache.get(b);
+    var aModule:Null<Module> = getModule(a);
+    var bModule:Null<Module> = getModule(b);
 
+    if (aModule == null || bModule == null)
+    {
+      return 0;
+    }
     if (aModule.priority != bModule.priority)
     {
       return aModule.priority - bModule.priority;
@@ -89,14 +94,14 @@ class ModuleHandler
     }
   }
 
-  public static function getModule(moduleId:String):Module
+  public static function getModule(moduleId:String):Null<Module>
   {
     return moduleCache.get(moduleId);
   }
 
   public static function activateModule(moduleId:String):Void
   {
-    var module:Module = getModule(moduleId);
+    var module:Null<Module> = getModule(moduleId);
     if (module != null)
     {
       module.active = true;
@@ -105,7 +110,7 @@ class ModuleHandler
 
   public static function deactivateModule(moduleId:String):Void
   {
-    var module:Module = getModule(moduleId);
+    var module:Null<Module> = getModule(moduleId);
     if (module != null)
     {
       module.active = false;
@@ -136,7 +141,7 @@ class ModuleHandler
   {
     for (moduleId in modulePriorityOrder)
     {
-      var module:Module = moduleCache.get(moduleId);
+      var module:Null<Module> = moduleCache.get(moduleId);
       // The module needs to be active to receive events.
       if (module != null && module.active)
       {