diff --git a/faust/tables/base.py b/faust/tables/base.py
index e3574ee21..ca26c0f11 100644
--- a/faust/tables/base.py
+++ b/faust/tables/base.py
@@ -382,13 +382,40 @@ async def _del_old_keys(self) -> None:
         for partition, timestamps in self._partition_timestamps.items():
             while timestamps and window.stale(timestamps[0], time.time()):
                 timestamp = heappop(timestamps)
+                triggered_windows = [
+                    self._partition_timestamp_keys.get(
+                        (partition, window_range)
+                    )  # noqa
+                    for window_range in self._window_ranges(timestamp)
+                ]
                 keys_to_remove = self._partition_timestamp_keys.pop(
                     (partition, timestamp), None
                 )
+                window_data = {}
                 if keys_to_remove:
-                    for key in keys_to_remove:
-                        value = self.data.pop(key, None)
-                        await self.on_window_close(key, value)
+                    for windows in triggered_windows:
+                        if windows:
+                            for processed_window in windows:
+                                # we use set to avoid duplicate element in window's data
+                                # window[0] is the window's key
+                                # it is not related to window's timestamp
+                                # windows are in format:
+                                # (key, (window_start, window_end))
+                                window_data.setdefault(processed_window[0], []).extend(
+                                    self.data.get(processed_window, [])
+                                )
+
+                    for key_to_remove in keys_to_remove:
+                        value = self.data.pop(key_to_remove, None)
+                        if key_to_remove[1][0] > self.last_closed_window:
+                            await self.on_window_close(
+                                key_to_remove,
+                                (
+                                    window_data[key_to_remove[0]]
+                                    if key_to_remove[0] in window_data
+                                    else value
+                                ),
+                            )
                     self.last_closed_window = max(
                         self.last_closed_window,
                         max(key[1][0] for key in keys_to_remove),
diff --git a/tests/unit/tables/test_base.py b/tests/unit/tables/test_base.py
index 84e800083..bcd6e5fd1 100644
--- a/tests/unit/tables/test_base.py
+++ b/tests/unit/tables/test_base.py
@@ -191,6 +191,45 @@ async def test_last_closed_window(self, *, table):
         assert table.last_closed_window == 0.0
 
         table.window = Mock(name="window")
+        self.mock_no_ranges(table)
+        table._data = {
+            ("boo", (1.1, 1.4)): "BOO",
+            ("moo", (1.4, 1.6)): "MOO",
+            ("faa", (1.9, 2.0)): "FAA",
+            ("bar", (4.1, 4.2)): "BAR",
+        }
+        table._partition_timestamps = {
+            TP1: [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0],
+        }
+        table._partition_timestamp_keys = {
+            (TP1, 2.0): [
+                ("boo", (1.1, 1.4)),
+                ("moo", (1.4, 1.6)),
+                ("faa", (1.9, 2.0)),
+            ],
+            (TP1, 5.0): [
+                ("bar", (4.1, 4.2)),
+            ],
+        }
+
+        def get_stale(limit):
+            def is_stale(timestamp, latest_timestamp):
+                return timestamp < limit
+
+            return is_stale
+
+        table.window.stale.side_effect = get_stale(4.0)
+
+        await table._del_old_keys()
+
+        assert table.last_closed_window == 1.9
+
+    @pytest.mark.asyncio
+    async def test_last_closed_window__mock_ranges(self, *, table):
+        assert table.last_closed_window == 0.0
+
+        table.window = Mock(name="window")
+        self.mock_ranges(table)
         table._data = {
             ("boo", (1.1, 1.4)): "BOO",
             ("moo", (1.4, 1.6)): "MOO",
@@ -233,6 +272,64 @@ async def test_del_old_keys(self, *, table):
         on_window_close = table._on_window_close = AsyncMock(name="on_window_close")
 
         table.window = Mock(name="window")
+        self.mock_no_ranges(table)
+        table._data = {
+            ("boo", (1.1, 1.4)): "BOO",
+            ("moo", (1.4, 1.6)): "MOO",
+            ("faa", (1.9, 2.0)): "FAA",
+            ("bar", (4.1, 4.2)): "BAR",
+        }
+        table._partition_timestamps = {
+            TP1: [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0],
+        }
+        table._partition_timestamp_keys = {
+            (TP1, 2.0): [
+                ("boo", (1.1, 1.4)),
+                ("moo", (1.4, 1.6)),
+                ("faa", (1.9, 2.0)),
+            ],
+            (TP1, 5.0): [
+                ("bar", (4.1, 4.2)),
+            ],
+        }
+
+        def get_stale(limit):
+            def is_stale(timestamp, latest_timestamp):
+                return timestamp < limit
+
+            return is_stale
+
+        table.window.stale.side_effect = get_stale(4.0)
+
+        await table._del_old_keys()
+
+        assert table._partition_timestamps[TP1] == [4.0, 5.0, 6.0, 7.0]
+        assert table.data == {("bar", (4.1, 4.2)): "BAR"}
+
+        on_window_close.assert_has_calls(
+            [
+                call.__bool__(),
+                call(("boo", (1.1, 1.4)), "BOO"),
+                call.__bool__(),
+                call(("moo", (1.4, 1.6)), "MOO"),
+                call.__bool__(),
+                call(("faa", (1.9, 2.0)), "FAA"),
+            ]
+        )
+
+        table.last_closed_window = 8.0
+        table.window.stale.side_effect = get_stale(6.0)
+
+        await table._del_old_keys()
+
+        assert not table.data
+
+    @pytest.mark.asyncio
+    async def test_del_old_keys__mock_ranges(self, *, table):
+        on_window_close = table._on_window_close = AsyncMock(name="on_window_close")
+
+        table.window = Mock(name="window")
+        self.mock_ranges(table)
         table._data = {
             ("boo", (1.1, 1.4)): "BOO",
             ("moo", (1.4, 1.6)): "MOO",
@@ -289,6 +386,61 @@ async def test_del_old_keys_non_async_cb(self, *, table):
         on_window_close = table._on_window_close = Mock(name="on_window_close")
 
         table.window = Mock(name="window")
+        self.mock_no_ranges(table)
+        table._data = {
+            ("boo", (1.1, 1.4)): "BOO",
+            ("moo", (1.4, 1.6)): "MOO",
+            ("faa", (1.9, 2.0)): "FAA",
+            ("bar", (4.1, 4.2)): "BAR",
+        }
+        table._partition_timestamps = {
+            TP1: [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0],
+        }
+        table._partition_timestamp_keys = {
+            (TP1, 2.0): [
+                ("boo", (1.1, 1.4)),
+                ("moo", (1.4, 1.6)),
+                ("faa", (1.9, 2.0)),
+            ],
+            (TP1, 5.0): [
+                ("bar", (4.1, 4.2)),
+            ],
+        }
+
+        def get_stale(limit):
+            def is_stale(timestamp, latest_timestamp):
+                return timestamp < limit
+
+            return is_stale
+
+        table.window.stale.side_effect = get_stale(4.0)
+
+        await table._del_old_keys()
+
+        assert table._partition_timestamps[TP1] == [4.0, 5.0, 6.0, 7.0]
+        assert table.data == {("bar", (4.1, 4.2)): "BAR"}
+
+        on_window_close.assert_has_calls(
+            [
+                call(("boo", (1.1, 1.4)), "BOO"),
+                call(("moo", (1.4, 1.6)), "MOO"),
+                call(("faa", (1.9, 2.0)), "FAA"),
+            ]
+        )
+
+        table.last_closed_window = 8.0
+        table.window.stale.side_effect = get_stale(6.0)
+
+        await table._del_old_keys()
+
+        assert not table.data
+
+    @pytest.mark.asyncio
+    async def test_del_old_keys_non_async_cb__mock_ranges(self, *, table):
+        on_window_close = table._on_window_close = Mock(name="on_window_close")
+
+        table.window = Mock(name="window")
+        self.mock_ranges(table)
         table._data = {
             ("boo", (1.1, 1.4)): "BOO",
             ("moo", (1.4, 1.6)): "MOO",
@@ -527,6 +679,11 @@ def mock_ranges(self, table, ranges=[1.1, 1.2, 1.3]):  # noqa
         table._window_ranges.return_value = ranges
         return ranges
 
+    def mock_no_ranges(self, table, ranges=[]):  # noqa
+        table._window_ranges = Mock(name="_window_ranges")
+        table._window_ranges.return_value = ranges
+        return ranges
+
     def test_relative_now(self, *, table):
         event = Mock(name="event", autospec=Event)
         table._partition_latest_timestamp[event.message.partition] = 30.3