diff --git a/tests/concurrency/sync.py b/tests/concurrency/sync.py
index aa31403..eec12dc 100644
--- a/tests/concurrency/sync.py
+++ b/tests/concurrency/sync.py
@@ -8,7 +8,7 @@
 client = ZeroClient("localhost", 5559)
 
 
-func = partial(client.call, "sleep")
+func = partial(client.call, "sleep_async")
 
 
 def get_and_print(msg):
diff --git a/zero/client_server/worker.py b/zero/client_server/worker.py
index 6e485df..e8d8bf2 100644
--- a/zero/client_server/worker.py
+++ b/zero/client_server/worker.py
@@ -8,6 +8,7 @@
 from zero.codegen.codegen import CodeGen
 from zero.encoder.protocols import Encoder
 from zero.error import SERVER_PROCESSING_ERROR
+from zero.utils.async_to_sync import async_to_sync
 from zero.zero_mq.factory import get_worker
 
 
@@ -80,7 +81,8 @@ def handle_msg(self, rpc, msg):
             # TODO: is this a bottleneck
             if inspect.iscoroutinefunction(func):
                 # this is blocking
-                ret = self._loop.run_until_complete(func(msg) if msg else func())
+                # ret = self._loop.run_until_complete(func(msg) if msg else func())
+                ret = async_to_sync(func)(msg) if msg else async_to_sync(func)()
             else:
                 ret = func(msg) if msg else func()
 
diff --git a/zero/utils/async_to_sync.py b/zero/utils/async_to_sync.py
new file mode 100644
index 0000000..91d3a56
--- /dev/null
+++ b/zero/utils/async_to_sync.py
@@ -0,0 +1,19 @@
+import asyncio
+import threading
+from functools import wraps
+
+_loop = asyncio.new_event_loop()
+
+_thrd = threading.Thread(target=_loop.run_forever, name="Async Runner", daemon=True)
+
+
+def async_to_sync(func):
+    @wraps(func)
+    def run(*args, **kwargs):
+        if not _thrd.is_alive():
+            _thrd.start()
+
+        future = asyncio.run_coroutine_threadsafe(func(*args, **kwargs), _loop)
+        return future.result()
+
+    return run