diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index dd2354b14a..091915857e 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -2202,11 +2202,15 @@ int stop_arrow(void)
     new_insert_skip = 2;
   } else if (ins_need_undo) {
     if (u_save_cursor() == OK) {
-      // A command or event may have moved the cursor or edited the
-      // buffer. Update Insstart so that later edits can properly decide
-      // whether an extra undo entry is needed.
-      Insstart = curwin->w_cursor;
-      Insstart_textlen = (colnr_T)linetabsize_str(get_cursor_line_ptr());
+      // A command or event may have moved the cursor before the next
+      // edit. Pull Insstart back only when the cursor moved above it,
+      // so that later edits can properly decide whether an extra undo
+      // entry is needed. Advancing Insstart would mis-place '[ after a
+      // register paste.
+      if (lt(curwin->w_cursor, Insstart)) {
+        Insstart = curwin->w_cursor;
+        Insstart_textlen = (colnr_T)linetabsize_str(get_cursor_line_ptr());
+      }
       ins_need_undo = false;
     }
   }
diff --git a/test/old/testdir/test_edit.vim b/test/old/testdir/test_edit.vim
index 4530e2116f..3a18266c91 100644
--- a/test/old/testdir/test_edit.vim
+++ b/test/old/testdir/test_edit.vim
@@ -2498,4 +2498,18 @@ func Test_autoindent_no_strip_after_cursorholdi()
   bwipe!
 endfunc
 
+" Issue #20130: '[ must mark the start of the paste after CTRL-R CTRL-P + edit.
+func Test_open_square_mark_after_ctrl_r_ctrl_p_paste()
+  new
+  call setline(1, ['a', 'b', 'c', 'd'])
+  call cursor(4, 1)
+
+  call feedkeys("Vggyjo\<C-r>\<C-p>\"\<BS>\<Esc>", 'xt')
+
+  call assert_equal(['a', 'b', 'a', 'b', 'c', 'd', 'c', 'd'],
+        \ getline(1, '$'))
+  call assert_equal([0, 3, 1, 0], getpos("'["))
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab