diff --git a/docs/changelog.rst b/docs/changelog.rst
index 1742b74b6..e11c93ccd 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -18,6 +18,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - macOS: Fix Spotlight search of global menu not working in non-English locales
   (:pull:`3567`)
 
+- Fix tab activity symbol not appearing if no other changes happen in tab bar even when
+  there is activity in a tab (:iss:`3571`)
+
 
 0.20.2 [2021-04-28]
 ----------------------
diff --git a/kitty/boss.py b/kitty/boss.py
index cc282a9fd..d89a1418e 100755
--- a/kitty/boss.py
+++ b/kitty/boss.py
@@ -768,6 +768,12 @@ class Boss:
                     cocoa_set_menubar_title(w.title or '')
             tm.mark_tab_bar_dirty()
 
+    def on_activity_since_last_focus(self, window: Window) -> None:
+        os_window_id = window.os_window_id
+        tm = self.os_window_map.get(os_window_id)
+        if tm is not None:
+            tm.mark_tab_bar_dirty()
+
     def update_tab_bar_data(self, os_window_id: int) -> None:
         tm = self.os_window_map.get(os_window_id)
         if tm is not None:
diff --git a/kitty/screen.c b/kitty/screen.c
index 99b957973..6a2dd0d80 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -571,6 +571,7 @@ screen_draw(Screen *self, uint32_t och, bool from_input_stream) {
     if (is_ignored_char(och)) return;
     if (!self->has_activity_since_last_focus && !self->has_focus) {
         self->has_activity_since_last_focus = true;
+        CALLBACK("on_activity_since_last_focus", NULL);
     }
     uint32_t ch = och < 256 ? self->g_charset[och] : och;
     bool is_cc = is_combining_char(ch);
diff --git a/kitty/window.py b/kitty/window.py
index ce82a9a47..439f5bbd6 100644
--- a/kitty/window.py
+++ b/kitty/window.py
@@ -612,6 +612,10 @@ class Window:
     def has_activity_since_last_focus(self) -> bool:
         return self.screen.has_activity_since_last_focus()
 
+    def on_activity_since_last_focus(self) -> None:
+        if self.opts.tab_activity_symbol:
+            get_boss().on_activity_since_last_focus(self)
+
     def on_bell(self) -> None:
         if self.opts.command_on_bell and self.opts.command_on_bell != ['none']:
             import shlex
diff --git a/kitty_tests/__init__.py b/kitty_tests/__init__.py
index 5c0c2f465..f141b3940 100644
--- a/kitty_tests/__init__.py
+++ b/kitty_tests/__init__.py
@@ -51,6 +51,9 @@ class Callbacks:
         self.notifications = []
         self.open_urls = []
 
+    def on_activity_since_last_focus(self) -> None:
+        pass
+
 
 def filled_line_buf(ynum=5, xnum=5, cursor=Cursor()):
     ans = LineBuf(ynum, xnum)