diff --git a/src/py/kaleido/_sync_server.py b/src/py/kaleido/_sync_server.py
index 740bd902..50eb804a 100644
--- a/src/py/kaleido/_sync_server.py
+++ b/src/py/kaleido/_sync_server.py
@@ -6,7 +6,8 @@
 from functools import partial
 from queue import Queue
 from threading import Thread
-from typing import TYPE_CHECKING, NamedTuple
+from typing import TYPE_CHECKING, NamedTuple, Any
+from concurrent.futures import Future
 
 from .kaleido import Kaleido
 
@@ -18,6 +19,7 @@ class Task(NamedTuple):
     fn: str
     args: Any
     kwargs: Any
+    future:Future[Any]
 
 
 class _BadFunctionName(BaseException):
@@ -37,11 +39,10 @@ async def _server(self, *args, **kwargs):
                 if not hasattr(k, task.fn):
                     raise _BadFunctionName(f"Kaleido has no attribute {task.fn}")
                 try:
-                    self._return_queue.put(
-                        await getattr(k, task.fn)(*task.args, **task.kwargs),
-                    )
+                    result = await getattr(k, task.fn)(*task.args, **task.kwargs)
+                    task.future.set_result(result)
                 except Exception as e:  # noqa: BLE001
-                    self._return_queue.put(e)
+                    task.future.set_exception(e)
 
                 self._task_queue.task_done()
 
@@ -72,7 +73,6 @@ def open(self, *args: Any, silence_warnings=False, **kwargs: Any) -> None:
             daemon=True,
         )
         self._task_queue: Queue[Task | None] = Queue()
-        self._return_queue: Queue[Any] = Queue()
         self._thread.start()
         self._initialized = True
         close = partial(self.close, silence_warnings=True)
@@ -92,7 +92,6 @@ def close(self, *, silence_warnings=False):
         self._thread.join()
         del self._thread
         del self._task_queue
-        del self._return_queue
         self._initialized = False
 
     def call_function(self, cmd: str, *args: Any, **kwargs: Any):
@@ -117,13 +116,9 @@ def call_function(self, cmd: str, *args: Any, **kwargs: Any):
                 UserWarning,
                 stacklevel=3,
             )
-        self._task_queue.put(Task(cmd, args, kwargs))
-        self._task_queue.join()
-        res = self._return_queue.get()
-        if isinstance(res, BaseException):
-            raise res
-        else:
-            return res
+        future:Future[Any] = Future()
+        self._task_queue.put(Task(cmd, args, kwargs,future))
+        return future.result()
 
 
 def oneshot_async_run(