diff --git a/ICSharpCode.AvalonEdit/Editing/RectangleSelection.cs b/ICSharpCode.AvalonEdit/Editing/RectangleSelection.cs
index 60888d88..2834b2e0 100644
--- a/ICSharpCode.AvalonEdit/Editing/RectangleSelection.cs
+++ b/ICSharpCode.AvalonEdit/Editing/RectangleSelection.cs
@@ -288,12 +288,15 @@ int GetVisualColumnFromXPos(int line, double xPos)
 		/// <inheritdoc/>
 		public override Selection UpdateOnDocumentChange(DocumentChangeEventArgs e)
 		{
-			TextLocation newStartLocation = textArea.Document.GetLocation(e.GetNewOffset(topLeftOffset, AnchorMovementType.AfterInsertion));
-			TextLocation newEndLocation = textArea.Document.GetLocation(e.GetNewOffset(bottomRightOffset, AnchorMovementType.BeforeInsertion));
-
-			return new RectangleSelection(textArea,
-										  new TextViewPosition(newStartLocation, GetVisualColumnFromXPos(newStartLocation.Line, startXPos)),
-										  new TextViewPosition(newEndLocation, GetVisualColumnFromXPos(newEndLocation.Line, endXPos)));
+			// we don't want to recalculate the whole selection, as this is called for every line within the selection
+			// and it can cause selection changes to take a wildly-long time.
+			return this;
+			//TextLocation newStartLocation = textArea.Document.GetLocation(e.GetNewOffset(topLeftOffset, AnchorMovementType.AfterInsertion));
+			//TextLocation newEndLocation = textArea.Document.GetLocation(e.GetNewOffset(bottomRightOffset, AnchorMovementType.BeforeInsertion));
+
+			//return new RectangleSelection(textArea,
+			//							  new TextViewPosition(newStartLocation, GetVisualColumnFromXPos(newStartLocation.Line, startXPos)),
+			//							  new TextViewPosition(newEndLocation, GetVisualColumnFromXPos(newEndLocation.Line, endXPos)));
 		}
 
 		/// <inheritdoc/>
@@ -331,7 +334,10 @@ public override void ReplaceSelectionWithText(string newText)
 					pos = new TextViewPosition(document.GetLocation(editOffset + firstInsertionLength));
 					textArea.ClearSelection();
 				}
-				textArea.Caret.Position = textArea.TextView.GetPosition(new Point(GetXPos(textArea, pos), textArea.TextView.GetVisualTopByDocumentLine(Math.Max(startLine, endLine)))).GetValueOrDefault();
+				TextViewPosition? calculatedPositon = textArea.TextView.GetPosition(new Point(GetXPos(textArea, pos), textArea.TextView.GetVisualTopByDocumentLine(Math.Max(startLine, endLine))));
+				if (calculatedPositon != null) {
+					textArea.Caret.Position = calculatedPositon.GetValueOrDefault();
+				}
 			}
 		}