diff --git a/fsspec/spec.py b/fsspec/spec.py
index da120e525..07d8cdca5 100644
--- a/fsspec/spec.py
+++ b/fsspec/spec.py
@@ -70,9 +70,12 @@ def __call__(cls, *args, **kwargs):
         strip_tokenize_options = {
             k: kwargs.pop(k) for k in cls._strip_tokenize_options if k in kwargs
         }
-        token = tokenize(
-            cls, cls._pid, threading.get_ident(), *args, *extra_tokens, **kwargs
-        )
+        if getattr(cls, "async_impl", False) and not kwargs.get("asynchronous", False):
+            token = tokenize(cls, cls._pid, *args, *extra_tokens, **kwargs)
+        else:
+            token = tokenize(
+                cls, cls._pid, threading.get_ident(), *args, *extra_tokens, **kwargs
+            )
         skip = kwargs.pop("skip_instance_cache", False)
         if os.getpid() != cls._pid:
             cls._cache.clear()
diff --git a/fsspec/tests/test_cache_threads.py b/fsspec/tests/test_cache_threads.py
new file mode 100644
index 000000000..eb279ea82
--- /dev/null
+++ b/fsspec/tests/test_cache_threads.py
@@ -0,0 +1,94 @@
+import threading
+
+import pytest
+
+import fsspec
+from fsspec.asyn import AsyncFileSystem
+from fsspec.registry import register_implementation
+from fsspec.spec import AbstractFileSystem
+
+
+class SyncDummyFS(AbstractFileSystem):
+    cachable = True
+    async_impl = False
+    protocol = "syncdummy"
+
+
+class AsyncDummyFS(AsyncFileSystem):
+    cachable = True
+    protocol = "asyncdummy"
+
+
+@pytest.fixture(autouse=True)
+def dummy_fs_setup():
+    register_implementation("syncdummy", SyncDummyFS)
+    register_implementation("asyncdummy", AsyncDummyFS)
+    SyncDummyFS.clear_instance_cache()
+    AsyncDummyFS.clear_instance_cache()
+    yield
+    SyncDummyFS.clear_instance_cache()
+    AsyncDummyFS.clear_instance_cache()
+
+
+def test_async_fs_sync_mode_shares_instance():
+    results = {}
+    lock = threading.Lock()
+
+    def worker(thread_id):
+        with lock:
+            fs = fsspec.filesystem("asyncdummy", asynchronous=False)
+        results[thread_id] = id(fs)
+
+    t1 = threading.Thread(target=worker, args=(1,))
+    t2 = threading.Thread(target=worker, args=(2,))
+
+    t1.start()
+    t2.start()
+    t1.join()
+    t2.join()
+
+    assert results[1] == results[2]
+
+
+def test_async_fs_async_mode_does_not_share():
+    results = {}
+    lock = threading.Lock()
+    barrier = threading.Barrier(2)
+
+    def worker(thread_id):
+        barrier.wait()
+        with lock:
+            fs = fsspec.filesystem("asyncdummy", asynchronous=True)
+        results[thread_id] = id(fs)
+
+    t1 = threading.Thread(target=worker, args=(1,))
+    t2 = threading.Thread(target=worker, args=(2,))
+
+    t1.start()
+    t2.start()
+    t1.join()
+    t2.join()
+
+    assert results[1] != results[2]
+
+
+def test_sync_fs_does_not_share():
+    results = {}
+    lock = threading.Lock()
+    barrier = threading.Barrier(2)
+
+    def worker(thread_id):
+        barrier.wait()
+        with lock:
+            fs = fsspec.filesystem("syncdummy")
+        results[thread_id] = id(fs)
+
+    t1 = threading.Thread(target=worker, args=(1,))
+    t2 = threading.Thread(target=worker, args=(2,))
+
+    t1.start()
+    t2.start()
+    t1.join()
+    t2.join()
+
+    assert results[1] != results[2]