diff --git a/src/Notepad3.c b/src/Notepad3.c
index 6b84efd9c..6833e0bc4 100644
--- a/src/Notepad3.c
+++ b/src/Notepad3.c
@@ -7040,6 +7040,7 @@ int BeginSelUndoAction()
   if (sel.currPos != sel.anchorPos) {
     token = UndoSelectionMap(-1, &sel);
     if (token >= 0) {
+      bModified = TRUE;
       SendMessage(hwndEdit, SCI_BEGINUNDOACTION, 0, 0);
       SendMessage(hwndEdit, SCI_ADDUNDOACTION, (WPARAM)token, 0);
     }