diff --git a/aw_watcher_window/main.py b/aw_watcher_window/main.py
index e271c70..bfb053e 100644
--- a/aw_watcher_window/main.py
+++ b/aw_watcher_window/main.py
@@ -25,6 +25,18 @@
     logger.setLevel(logging.__getattribute__(log_level.upper()))
 
 
+def compute_pulsetime(poll_time: float) -> float:
+    """Scale pulsetime with poll_time so OS scheduling jitter doesn't break heartbeat chains.
+
+    At poll_time=1s, jitter ~0.15s is well within 1s margin (poll_time+1).
+    At poll_time=5s, jitter ~0.75s exceeds the 1s margin ~10% of the time,
+    causing missing time in the timeline. max(poll_time*1.5, poll_time+1) keeps
+    backward compatibility at poll_time≤2s while fixing the problem at higher
+    polling intervals. See: https://github.com/ActivityWatch/activitywatch/issues/1177
+    """
+    return max(poll_time * 1.5, poll_time + 1.0)
+
+
 def kill_process(pid):
     logger.info("Killing process {}".format(pid))
     try:
@@ -157,11 +169,11 @@ def heartbeat_loop(
             now = datetime.now(timezone.utc)
             current_window_event = Event(timestamp=now, data=current_window)
 
-            # Set pulsetime to 1 second more than the poll_time
-            # This since the loop takes more time than poll_time
-            # due to sleep(poll_time).
             client.heartbeat(
-                bucket_id, current_window_event, pulsetime=poll_time + 1.0, queued=True
+                bucket_id,
+                current_window_event,
+                pulsetime=compute_pulsetime(poll_time),
+                queued=True,
             )
 
         sleep(poll_time)
diff --git a/tests/test_main.py b/tests/test_main.py
index 96e04b1..e8b5be0 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -1,3 +1,6 @@
+import pytest
+
+from aw_watcher_window.main import compute_pulsetime
 from aw_watcher_window.macos_cli import build_swift_command
 
 
@@ -42,3 +45,23 @@ def test_build_swift_command_passes_title_filters():
         "--exclude-titles",
         "Slack.*huddle",
     ]
+
+
+@pytest.mark.parametrize(
+    "poll_time,expected_pulsetime",
+    [
+        (1.0, 2.0),   # max(1.5, 2.0)=2.0 — backward compatible, no change
+        (2.0, 3.0),   # max(3.0, 3.0)=3.0 — exact threshold
+        (5.0, 7.5),   # max(7.5, 6.0)=7.5 — fix kicks in (was 6.0, caused ~10% loss)
+        (10.0, 15.0), # max(15.0, 11.0)=15.0 — fix kicks in (was 11.0, caused ~30% loss)
+    ],
+)
+def test_pulsetime_scales_with_poll_time(poll_time: float, expected_pulsetime: float):
+    """pulsetime must scale with poll_time so OS scheduling jitter doesn't break heartbeat chains.
+
+    At poll_time=5s the old formula (poll_time+1=6s) caused ~10% of heartbeat
+    gaps to exceed pulsetime, resulting in missing time. The fix: max(poll_time*1.5,
+    poll_time+1) keeps backward compat at low poll_time while scaling the jitter
+    tolerance at higher values. See: ActivityWatch/activitywatch#1177
+    """
+    assert compute_pulsetime(poll_time) == expected_pulsetime