diff --git a/src/BizHawk.Client.Common/movie/tasproj/TasMovie.Editing.cs b/src/BizHawk.Client.Common/movie/tasproj/TasMovie.Editing.cs
index 4c8af50ffc..b67de61568 100644
--- a/src/BizHawk.Client.Common/movie/tasproj/TasMovie.Editing.cs
+++ b/src/BizHawk.Client.Common/movie/tasproj/TasMovie.Editing.cs
@@ -258,19 +258,16 @@ namespace BizHawk.Client.Common
 		private void ExtendMovieForEdit(int numFrames)
 		{
 			int oldLength = InputLogLength;
-			ChangeLog.AddGeneralUndo(oldLength, oldLength + numFrames - 1);
 
-			Session.MovieController.SetFrom(Session.StickySource);
-
-			// account for autohold. needs autohold pattern to be already recorded in the current frame
+			// account for autohold TODO: What about auto-fire?
+			string inputs = Bk2LogEntryGenerator.GenerateLogEntry(Session.StickySource);
 			for (int i = 0; i < numFrames; i++)
 			{
-				Log.Add(Bk2LogEntryGenerator.GenerateLogEntry(Session.MovieController));
+				Log.Add(inputs);
 			}
 
 			Changes = true;
-
-			ChangeLog.SetGeneralRedo();
+			ChangeLog.AddExtend(oldLength, numFrames, inputs);
 		}
 
 		public void ToggleBoolState(int frame, string buttonName)
diff --git a/src/BizHawk.Client.Common/movie/tasproj/TasMovie.History.cs b/src/BizHawk.Client.Common/movie/tasproj/TasMovie.History.cs
index e0a77d7a9e..ce73e23a4d 100644
--- a/src/BizHawk.Client.Common/movie/tasproj/TasMovie.History.cs
+++ b/src/BizHawk.Client.Common/movie/tasproj/TasMovie.History.cs
@@ -29,6 +29,7 @@ namespace BizHawk.Client.Common
 		void AddInsertFrames(int frame, int count, string name = "", bool force = false);
 		void AddInsertInput(int frame, List<string> newInputs, string name = "", bool force = false);
 		void AddRemoveFrames(int removeStart, int removeUpTo, List<string> oldInputs, List<TasMovieMarker> removedMarkers, string name = "", bool force = false);
+		void AddExtend(int originalLength, int count, string inputs);
 	}
 
 	public class TasMovieChangeLog : IMovieChangeLog
@@ -380,6 +381,15 @@ namespace BizHawk.Client.Common
 				LatestBatch.Add(new MovieActionRemoveFrames(removeStart, removeUpTo, oldInputs, removedMarkers));
 			}
 		}
+
+		public void AddExtend(int originalLength, int count, string inputs)
+		{
+			if (IsRecording)
+			{
+				AddMovieAction("extend movie");
+				LatestBatch.Add(new MovieActionExtend(originalLength, count, inputs));
+			}
+		}
 	}
 
 	public interface IMovieAction
@@ -844,4 +854,47 @@ namespace BizHawk.Client.Common
 			movie.ChangeLog.IsRecording = wasRecording;
 		}
 	}
+
+
+	public class MovieActionExtend : IMovieAction
+	{
+		public int FirstFrame { get; }
+		public int LastFrame => FirstFrame + _count - 1;
+
+		private int _count;
+		private string _inputs;
+
+		public MovieActionExtend(int currentEndOfMovie, int count, string inputs)
+		{
+			FirstFrame = currentEndOfMovie;
+			_count = count;
+			_inputs = inputs;
+		}
+
+		public void Undo(ITasMovie movie)
+		{
+			bool wasRecording = movie.ChangeLog.IsRecording;
+			movie.ChangeLog.IsRecording = false;
+			bool wasMarkerBound = movie.BindMarkersToInput;
+			movie.BindMarkersToInput = false;
+
+			movie.RemoveFrames(FirstFrame, LastFrame + 1);
+
+			movie.ChangeLog.IsRecording = wasRecording;
+			movie.BindMarkersToInput = wasMarkerBound;
+		}
+
+		public void Redo(ITasMovie movie)
+		{
+			bool wasRecording = movie.ChangeLog.IsRecording;
+			movie.ChangeLog.IsRecording = false;
+			bool wasMarkerBound = movie.BindMarkersToInput;
+			movie.BindMarkersToInput = false;
+
+			movie.InsertInput(FirstFrame, Enumerable.Repeat(_inputs, _count));
+
+			movie.ChangeLog.IsRecording = wasRecording;
+			movie.BindMarkersToInput = wasMarkerBound;
+		}
+	}
 }