diff --git a/Editor/Module Management/ModuleInstaller.cs b/Editor/Module Management/ModuleInstaller.cs
index 5b2d5e28..f894ea0b 100644
--- a/Editor/Module Management/ModuleInstaller.cs	
+++ b/Editor/Module Management/ModuleInstaller.cs	
@@ -22,8 +22,6 @@ public static class ModuleInstaller
 
         private const int THREAD_SLEEP_TIME = 100;
         private const string PROGRESS_BAR_TITLE = "Ready Player Me";
-        private const string GLTFAST_SYMBOL = "GLTFAST";
-        private const string READY_PLAYER_ME_SYMBOL = "READY_PLAYER_ME";
         private const string GLTFAST_NAME = "com.atteneder.gltfast";
         private const string WEBVIEW_NAME = "webview";
 
@@ -39,6 +37,8 @@ public static class ModuleInstaller
 
         static ModuleInstaller()
         {
+            Events.registeringPackages -= OnRegisteringPackages;
+            Events.registeringPackages += OnRegisteringPackages;
 # if RPM_DEVELOPMENT
             modulesInstalled = true;
 #endif
@@ -47,16 +47,29 @@ static ModuleInstaller()
                 InstallModules();
                 EditorApplication.delayCall += DelayCreateCoreSettings;
             }
-
+            
 #if !GLTFAST
             if (IsModuleInstalled(GLTFAST_NAME))
             {
-                AddGltfastSymbol();
-                AddScriptingDefineSymbolToAllBuildTargetGroups(READY_PLAYER_ME_SYMBOL);
+                DefineSymbolHelper.AddSymbols();
             }
 #endif
 
         }
+        
+        /// <summary>
+        ///     Called when a package is about to be added, removed or changed.
+        /// </summary>
+        /// <param name="args">Describes the <c>PackageInfo</c> entries of packages currently registering.</param>
+        private static void OnRegisteringPackages(PackageRegistrationEventArgs args)
+        {
+            // Core module uninstalled
+            if (args.removed != null && args.removed.Any(p => p.name == ModuleList.Core.name))
+            {
+                DefineSymbolHelper.RemoveSymbols();
+                ProjectPrefs.SetBool(ProjectPrefs.FIRST_TIME_SETUP_DONE, false);
+            }
+        }
 
         private static void DelayCreateCoreSettings()
         {
@@ -158,39 +171,6 @@ public static PackageInfo[] GetPackageList()
             return listRequest.Result.ToArray();
         }
 
-        public static void AddGltfastSymbol()
-        {
-            AddScriptingDefineSymbolToAllBuildTargetGroups(GLTFAST_SYMBOL);
-        }
-
-        private static void AddScriptingDefineSymbolToAllBuildTargetGroups(string defineSymbol)
-        {
-            foreach (BuildTarget target in Enum.GetValues(typeof(BuildTarget)))
-            {
-                BuildTargetGroup group = BuildPipeline.GetBuildTargetGroup(target);
-
-                if (group == BuildTargetGroup.Unknown)
-                {
-                    continue;
-                }
-
-                List<string> defineSymbols = PlayerSettings.GetScriptingDefineSymbolsForGroup(group).Split(';').Select(d => d.Trim()).ToList();
-
-                if (defineSymbols.Contains(defineSymbol)) continue;
-                defineSymbols.Add(defineSymbol);
-                try
-                {
-                    PlayerSettings.SetScriptingDefineSymbolsForGroup(group, string.Join(";", defineSymbols.ToArray()));
-                }
-                catch (Exception e)
-                {
-                    Debug.LogWarning("Could not set RPM " + defineSymbol + " defines for build target: " + target + " group: " + group + " " + e);
-                }
-            }
-
-            CompilationPipeline.RequestScriptCompilation();
-        }
-
         /// <summary>
         ///     Check all modules installed successfully
         /// </summary>
diff --git a/Editor/UI/EditorWindows/AvatarLoaderEditor/AvatarLoaderEditor.cs b/Editor/UI/EditorWindows/AvatarLoaderEditor/AvatarLoaderEditor.cs
index 864cb291..25a2d483 100644
--- a/Editor/UI/EditorWindows/AvatarLoaderEditor/AvatarLoaderEditor.cs
+++ b/Editor/UI/EditorWindows/AvatarLoaderEditor/AvatarLoaderEditor.cs
@@ -29,7 +29,7 @@ public class AvatarLoaderEditor : EditorWindow
         public static void ShowWindow()
         {
 #if !GLTFAST
-            ModuleInstaller.AddGltfastSymbol();
+            DefineSymbolHelper.AddSymbols();
 #endif
             var window = GetWindow<AvatarLoaderEditor>();
             window.titleContent = new GUIContent(AVATAR_LOADER);
diff --git a/Editor/Utils/DefineSymbolHelper.cs b/Editor/Utils/DefineSymbolHelper.cs
new file mode 100644
index 00000000..9a0bcdd5
--- /dev/null
+++ b/Editor/Utils/DefineSymbolHelper.cs
@@ -0,0 +1,72 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using UnityEngine;
+using UnityEditor;
+using UnityEditor.Compilation;
+
+namespace ReadyPlayerMe.Core.Editor
+{
+    public static class DefineSymbolHelper
+    {
+        private const string GLTFAST_SYMBOL = "GLTFAST";
+        private const string READY_PLAYER_ME_SYMBOL = "READY_PLAYER_ME";
+        
+        private static void ModifyScriptingDefineSymbolInAllBuildTargetGroups(string defineSymbol, bool addSymbol)
+        {
+            foreach (BuildTarget target in Enum.GetValues(typeof(BuildTarget)))
+            {
+                BuildTargetGroup group = BuildPipeline.GetBuildTargetGroup(target);
+
+                if (group == BuildTargetGroup.Unknown)
+                {
+                    continue;
+                }
+
+                List<string> defineSymbols = PlayerSettings.GetScriptingDefineSymbolsForGroup(group).Split(';').Select(d => d.Trim()).ToList();
+
+                if (addSymbol && !defineSymbols.Contains(defineSymbol))
+                {
+                    defineSymbols.Add(defineSymbol);
+                }
+                else if (!addSymbol && defineSymbols.Contains(defineSymbol))
+                {
+                    defineSymbols.Remove(defineSymbol);
+                }
+                else
+                {
+                    continue;
+                }
+
+                try
+                {
+                    PlayerSettings.SetScriptingDefineSymbolsForGroup(group, string.Join(";", defineSymbols.ToArray()));
+                }
+                catch (Exception e)
+                {
+                    var actionWord = addSymbol ? "set" : "remove";
+                    Debug.LogWarning($"Could not {actionWord} {defineSymbol} defines for build target: {target} group: {group} {e}");
+                }
+            }
+
+            if (addSymbol)
+            {
+                CompilationPipeline.RequestScriptCompilation();
+            }
+        }
+        
+        public static void AddSymbols()
+        {
+            ModifyScriptingDefineSymbolInAllBuildTargetGroups(GLTFAST_SYMBOL, true);
+            ModifyScriptingDefineSymbolInAllBuildTargetGroups(READY_PLAYER_ME_SYMBOL, true);
+            CompilationPipeline.RequestScriptCompilation();
+        }
+        
+        public static void RemoveSymbols()
+        {
+            ModifyScriptingDefineSymbolInAllBuildTargetGroups(GLTFAST_SYMBOL, false);
+            ModifyScriptingDefineSymbolInAllBuildTargetGroups(READY_PLAYER_ME_SYMBOL, false);
+        }
+        
+    }
+}
diff --git a/Editor/Utils/DefineSymbolHelper.cs.meta b/Editor/Utils/DefineSymbolHelper.cs.meta
new file mode 100644
index 00000000..27d0197c
--- /dev/null
+++ b/Editor/Utils/DefineSymbolHelper.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: f7f640bcb9cd21648a78581c77d76723
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: