diff --git a/runtime/doc/ui.txt b/runtime/doc/ui.txt
index a40ce928e8..781d759c82 100644
--- a/runtime/doc/ui.txt
+++ b/runtime/doc/ui.txt
@@ -642,6 +642,13 @@ tabs.
 	purpose it only counts "virtual" or "displayed" lines, so folds
 	only count as one line.
 
+	All updates, such as `grid_line`, in a batch affects the new viewport,
+	despite the fact that `win_viewport` is received after the updates.
+	Applications implementing, for example, smooth scrolling should take
+	this into account and keep the grid separated from what's displayed on
+	the screen and copy it to the viewport destination once `win_viewport`
+	is received.
+
 ["win_extmark", grid, win, ns_id, mark_id, row, col] ~
 	Updates the position of an extmark which is currently visible in a
 	window. Only emitted if the mark has the `ui_watched` attribute. 
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 0fe5d68c9e..26c533f2a3 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -987,7 +987,9 @@ void ui_ext_win_position(win_T *wp, bool validate)
 
 void ui_ext_win_viewport(win_T *wp)
 {
-  if ((wp == curwin || ui_has(kUIMultigrid)) && wp->w_viewport_invalid) {
+  // NOTE: The win_viewport command is delayed until the next flush when there are pending updates.
+  // This ensures that the updates and the viewport are sent together.
+  if ((wp == curwin || ui_has(kUIMultigrid)) && wp->w_viewport_invalid && wp->w_redr_type == 0) {
     int botline = wp->w_botline;
     int line_count = wp->w_buffer->b_ml.ml_line_count;
     if (botline == line_count + 1 && wp->w_empty_rows == 0) {