diff --git a/src/xpra/server/source.py b/src/xpra/server/source.py
index 3761acac05..11b0fbe3ee 100644
--- a/src/xpra/server/source.py
+++ b/src/xpra/server/source.py
@@ -1548,7 +1548,7 @@ def send_clipboard(self, packet):
                 self.send_clipboard_enabled(msg)
                 return
         #call compress_clibboard via the work queue:
-        self.encode_work_queue.put((self.compress_clipboard, packet))
+        self.encode_work_queue.put((True, self.compress_clipboard, packet))
 
     def compress_clipboard(self, packet):
         #Note: this runs in the 'encode' thread!
@@ -2122,8 +2122,13 @@ def encode_loop(self):
             fn_and_args = self.encode_work_queue.get(True)
             if fn_and_args is None:
                 return              #empty marker
+            #some function calls are optional and can be skipped when closing:
+            #(but some are not, like encoder clean functions)
+            optional_when_closing = fn_and_args[0]
+            if optional_when_closing and self.is_closed():
+                continue
             try:
-                fn_and_args[0](*fn_and_args[1:])
+                fn_and_args[1](*fn_and_args[2:])
             except Exception as e:
                 if self.is_closed():
                     log("ignoring encoding error in %s as source is already closed:", fn_and_args[0])
diff --git a/src/xpra/server/window/window_source.py b/src/xpra/server/window/window_source.py
index 390c81ce1d..31fb54ae04 100644
--- a/src/xpra/server/window/window_source.py
+++ b/src/xpra/server/window/window_source.py
@@ -518,7 +518,7 @@ def send_window_icon(self, window):
                 #and delay sending it by a bit to allow basic icon batching:
                 delay = max(50, int(self.batch_config.delay))
                 iconlog("send_window_icon(%s) wid=%s, icon=%s, compression scheduled in %sms", window, self.wid, surf, delay)
-                self.timeout_add(delay, self.call_in_encode_thread, self.compress_and_send_window_icon)
+                self.timeout_add(delay, self.call_in_encode_thread, True, self.compress_and_send_window_icon)
 
     def compress_and_send_window_icon(self):
         #this runs in the work queue
@@ -1350,20 +1350,20 @@ def process_damage_region(self, damage_time, window, x, y, w, h, coding, options
         av_sync = options.get("av-sync", False)
         av_delay = self.av_sync_delay*int(av_sync)
         if not av_sync:
-            self.call_in_encode_thread(self.make_data_packet_cb, *item)
+            self.call_in_encode_thread(True, self.make_data_packet_cb, *item)
         else:
             #schedule encode via queue, after freezing the pixels:
             if not image.freeze():
                 avsynclog("Warning: failed to freeze image pixels for:")
                 avsynclog(" %s", image)
-                self.call_in_encode_thread(self.make_data_packet_cb, *item)
+                self.call_in_encode_thread(True, self.make_data_packet_cb, *item)
                 return
             self.encode_queue.append(item)
             l = len(self.encode_queue)
             if l>=self.encode_queue_max_size:
                 av_delay = 0        #we must free some space!
             avsynclog("scheduling encode queue iteration in %ims, encode queue size=%i (max=%i)", av_delay, l, self.encode_queue_max_size)
-            self.timeout_add(av_delay, self.call_in_encode_thread, self.encode_from_queue)
+            self.timeout_add(av_delay, self.call_in_encode_thread, True, self.encode_from_queue)
 
     def encode_from_queue(self):
         #note: we use a queue here to ensure we preserve the order
@@ -1413,7 +1413,7 @@ def encode_from_queue(self):
             return
         first_due = int(max(0, min(still_due)-time.time())*1000)
         avsynclog("encode_from_queue: first due in %ims, due list=%s", first_due, still_due)
-        self.timeout_add(first_due, self.call_in_encode_thread, self.encode_from_queue)
+        self.timeout_add(first_due, self.call_in_encode_thread, True, self.encode_from_queue)
 
 
     def make_data_packet_cb(self, window, w, h, damage_time, process_damage_time, wid, image, coding, sequence, options, flush):
diff --git a/src/xpra/server/window/window_video_source.py b/src/xpra/server/window/window_video_source.py
index 99c06c1505..9297d08113 100644
--- a/src/xpra/server/window/window_video_source.py
+++ b/src/xpra/server/window/window_video_source.py
@@ -234,14 +234,14 @@ def csc_encoder_clean(self):
         csce = self._csc_encoder
         if csce:
             self._csc_encoder = None
-            self.call_in_encode_thread(csce.clean)
+            self.call_in_encode_thread(False, csce.clean)
 
     def video_encoder_clean(self):
         """ Calls self._video_encoder.clean() from the encode thread """
         ve = self._video_encoder
         if ve:
             self._video_encoder = None
-            self.call_in_encode_thread(ve.clean)
+            self.call_in_encode_thread(False, ve.clean)
 
 
     def parse_csc_modes(self, full_csc_modes):