diff --git a/python/ray/worker.py b/python/ray/worker.py
index b50e1d985..03d7fd6e8 100644
--- a/python/ray/worker.py
+++ b/python/ray/worker.py
@@ -1028,8 +1028,6 @@ def _initialize_serialization(worker=global_worker):
         _register_class(RayGetArgumentError)
         # Tell Ray to serialize lambdas with pickle.
         _register_class(type(lambda: 0), pickle=True)
-        # Tell Ray to serialize sets with pickle.
-        _register_class(type(set()), pickle=True)
         # Tell Ray to serialize types with pickle.
         _register_class(type(int), pickle=True)
 
diff --git a/src/thirdparty/download_thirdparty.sh b/src/thirdparty/download_thirdparty.sh
index bb82a656e..c0c32e620 100755
--- a/src/thirdparty/download_thirdparty.sh
+++ b/src/thirdparty/download_thirdparty.sh
@@ -13,4 +13,4 @@ fi
 cd $TP_DIR/arrow
 git fetch origin master
 
-git checkout b1e56a2f5d3fef3d04093fcfd4f279290f597d06
+git checkout 0c8853f90612b485c853cb54acf34a820591ca1d