diff --git a/CHANGES.rst b/CHANGES.rst
index 8d025e03d..a52176b74 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -13,6 +13,9 @@
 - Fix bug that caused result of ``set_array_compression`` to be overwritten by
   ``all_array_compression`` argument to ``write_to``. [#510]
 
+- Add workaround for Python OSX write limit bug
+  (see https://bugs.python.org/issue24658). [#521]
+
 2.0.1 (2018-05-08)
 ------------------
 
diff --git a/asdf/generic_io.py b/asdf/generic_io.py
index cd70e6b58..d7d06bc91 100644
--- a/asdf/generic_io.py
+++ b/asdf/generic_io.py
@@ -107,7 +107,11 @@ def _array_tofile_simple(fd, write, array):
 
 if sys.platform == 'darwin':  # pragma: no cover
     def _array_tofile(fd, write, array):
-        OSX_WRITE_LIMIT = 2 ** 32
+        # This value is currently set as a workaround for a known bug in Python
+        # on OSX. Individual writes must be less than 2GB, which necessitates
+        # the chunk size here if we want it to remain a power of 2.
+        # See https://bugs.python.org/issue24658.
+        OSX_WRITE_LIMIT = 2 ** 30
         if fd is None or array.nbytes >= OSX_WRITE_LIMIT and array.nbytes % 4096 == 0:
             return _array_tofile_chunked(write, array, OSX_WRITE_LIMIT)
         return _array_tofile_simple(fd, write, array)