diff --git a/src/HexManiac.Core/Core/Autos/StubDataModel.cs b/src/HexManiac.Core/Core/Autos/StubDataModel.cs
index 4b74d27f..b4484c07 100644
--- a/src/HexManiac.Core/Core/Autos/StubDataModel.cs
+++ b/src/HexManiac.Core/Core/Autos/StubDataModel.cs
@@ -32,6 +32,8 @@ namespace HavenSoft.HexManiac.Core.Models
             }
         }
 
+        public int ReferenceCount { get; set; }
+
         public bool SpartanMode { get; set; }
 
         public delegate System.Collections.Generic.IEnumerable<T> AllDelegate_<T>() where T : Runs.IFormattedRun;
diff --git a/src/HexManiac.Core/Models/IDataModel.cs b/src/HexManiac.Core/Models/IDataModel.cs
index 3241156c..29e18036 100644
--- a/src/HexManiac.Core/Models/IDataModel.cs
+++ b/src/HexManiac.Core/Models/IDataModel.cs
@@ -20,6 +20,7 @@ namespace HavenSoft.HexManiac.Core.Models {
 
       byte[] RawData { get; }
       ModelCacheScope CurrentCacheScope { get; }
+      int ReferenceCount { get; set; }
       bool SpartanMode { get; set; }
       bool HasChanged(int index);
       int ChangeCount { get; }
@@ -148,6 +149,8 @@ namespace HavenSoft.HexManiac.Core.Models {
          }
       }
 
+      public int ReferenceCount { get; set; } = 0; // used for tracking how many ViewModels currently use this Model
+
       public BaseModel(byte[] data) {
          RawData = data;
          var code = data.GetGameCode();
diff --git a/src/HexManiac.Core/ViewModels/ChildViewPort.cs b/src/HexManiac.Core/ViewModels/ChildViewPort.cs
index a0f25618..28030fde 100644
--- a/src/HexManiac.Core/ViewModels/ChildViewPort.cs
+++ b/src/HexManiac.Core/ViewModels/ChildViewPort.cs
@@ -22,6 +22,7 @@ namespace HavenSoft.HexManiac.Core.ViewModels {
          ScrollRegion.DeferHeader();
          Parent = viewPort;
          Width = Parent.Width;
+         viewPort.Model.ReferenceCount -= 1; // don't reference count child viewports
       }
 
       public void RefreshHeaders() => ScrollRegion.UpdateDeferedHeader();
diff --git a/src/HexManiac.Core/ViewModels/ViewPort.cs b/src/HexManiac.Core/ViewModels/ViewPort.cs
index 9993195b..25a97ea8 100644
--- a/src/HexManiac.Core/ViewModels/ViewPort.cs
+++ b/src/HexManiac.Core/ViewModels/ViewPort.cs
@@ -676,7 +676,7 @@ namespace HavenSoft.HexManiac.Core.ViewModels {
       }
 
       private void CloseExecuted(IFileSystem fileSystem) {
-         if (!history.IsSaved && ownsHistory) {
+         if (!history.IsSaved && Model.ReferenceCount == 1) {
             var metadata = Model.ExportMetadata(RefTable, Singletons.MetadataInfo);
             var result = fileSystem.TrySavePrompt(new LoadedFile(FileName, Model.RawData));
             if (result == null) return;
@@ -685,6 +685,8 @@ namespace HavenSoft.HexManiac.Core.ViewModels {
                history.TagAsSaved();
             }
          }
+         Model.ReferenceCount -= 1;
+
          Closed.Raise(this);
       }
 
@@ -1041,6 +1043,7 @@ namespace HavenSoft.HexManiac.Core.ViewModels {
          }
          PythonTool = pythonTool;
          ownsHistory = changeHistory == null;
+         model.ReferenceCount += 1;
 
          history = changeHistory ?? new ChangeHistory<ModelDelta>(RevertChanges);
          history.PropertyChanged += HistoryPropertyChanged;