diff --git a/src/scriptworker/context.py b/src/scriptworker/context.py
index a57eb0f3..8a5d04df 100644
--- a/src/scriptworker/context.py
+++ b/src/scriptworker/context.py
@@ -59,7 +59,7 @@ class Context(object):
 
     config: Optional[Dict[str, Any]] = None
     credentials_timestamp: Optional[int] = None
-    credentials_fd: int = -1
+    credentials_file = None
     proc: Optional[task_process.TaskProcess] = None
     queue: Optional[Queue] = None
     session: Optional[aiohttp.ClientSession] = None
@@ -99,8 +99,7 @@ def claim_task(self, claim_task: Optional[Dict[str, Any]]) -> None:
         if claim_task:
             self.task = claim_task["task"]
             self.verify_task()
-            # flags=0 to let the child inherit this fd
-            self.credentials_fd = os.memfd_create("scriptworker_temp_creds", flags=0)
+            self.credentials_file = tempfile.TemporaryFile()
             self.temp_credentials = claim_task["credentials"]
             path = os.path.join(self.config["work_dir"], "task.json")
             assert self.task
@@ -108,8 +107,9 @@ def claim_task(self, claim_task: Optional[Dict[str, Any]]) -> None:
         else:
             self.temp_credentials = None
             self.task = None
-            os.close(self.credentials_fd)
-            self.credentials_fd = -1
+            if self.credentials_file is not None:
+                self.credentials_file.close()
+                self.credentials_file = None
 
     def verify_task(self) -> None:
         """Run some task sanity checks on ``self.task``."""
@@ -201,7 +201,7 @@ def temp_credentials(self, credentials: Optional[Dict[str, Any]]) -> None:
         if credentials:
             data = json.dumps(credentials, indent=2, sort_keys=True).encode("ascii")
             # use pwrite so we don't confuse the child by changing the file offset
-            assert os.pwrite(self.credentials_fd, data, 0) == len(data)
+            assert os.pwrite(self.credentials_file.fileno(), data, 0) == len(data)
 
     def write_json(self, path: str, contents: Dict[str, Any], message: str) -> None:
         """Write json to disk.
diff --git a/src/scriptworker/task.py b/src/scriptworker/task.py
index ad0e8d69..19fc6660 100644
--- a/src/scriptworker/task.py
+++ b/src/scriptworker/task.py
@@ -672,7 +672,8 @@ async def run_task(context, to_cancellable_process):
     env["TASK_ID"] = context.task_id or "None"
     env["RUN_ID"] = str(get_run_id(context.claim_task))
     env["TASKCLUSTER_ROOT_URL"] = context.config["taskcluster_root_url"]
-    env["TASKCLUSTER_CREDENTIALS_FD"] = str(context.credentials_fd)
+    credentials_fd = context.credentials_file.fileno()
+    env["TASKCLUSTER_CREDENTIALS_FD"] = str(credentials_fd)
     kwargs = {
         "stdout": PIPE,
         "stderr": PIPE,
@@ -680,7 +681,7 @@ async def run_task(context, to_cancellable_process):
         "close_fds": True,
         "preexec_fn": lambda: os.setsid(),
         "env": env,
-        "pass_fds": (context.credentials_fd,),
+        "pass_fds": (credentials_fd,),
     }  # pragma: no branch
 
     timeout = get_task_maxruntime(context.task, context.config["task_max_timeout"])
diff --git a/tests/test_context.py b/tests/test_context.py
index 5549262c..eaad1f4f 100644
--- a/tests/test_context.py
+++ b/tests/test_context.py
@@ -77,42 +77,42 @@ async def test_set_reset_task(rw_context, claim_task, reclaim_task):
     assert rw_context.temp_queue is None
 
 
-def test_credentials_fd_initial(rw_context):
-    assert rw_context.credentials_fd == -1
+def test_credentials_file_initial(rw_context):
+    assert rw_context.credentials_file is None
 
 
 @pytest.mark.asyncio
-async def test_credentials_fd_opened_on_claim_task(rw_context, claim_task):
+async def test_credentials_file_opened_on_claim_task(rw_context, claim_task):
     rw_context.claim_task = claim_task
-    assert rw_context.credentials_fd >= 0
-    os.fstat(rw_context.credentials_fd)  # raises OSError if fd is invalid
+    assert rw_context.credentials_file is not None
+    os.fstat(rw_context.credentials_file.fileno())  # raises OSError if fd is invalid
 
 
 @pytest.mark.asyncio
-async def test_credentials_fd_content(rw_context, claim_task):
+async def test_credentials_file_content(rw_context, claim_task):
     rw_context.claim_task = claim_task
-    fd = rw_context.credentials_fd
+    fd = rw_context.credentials_file.fileno()
     size = os.fstat(fd).st_size
     data = os.pread(fd, size, 0)
     assert json.loads(data) == claim_task["credentials"]
 
 
 @pytest.mark.asyncio
-async def test_credentials_fd_updated_on_reclaim(rw_context, claim_task, reclaim_task):
+async def test_credentials_file_updated_on_reclaim(rw_context, claim_task, reclaim_task):
     rw_context.claim_task = claim_task
     rw_context.reclaim_task = reclaim_task
-    fd = rw_context.credentials_fd
+    fd = rw_context.credentials_file.fileno()
     size = os.fstat(fd).st_size
     data = os.pread(fd, size, 0)
     assert json.loads(data) == reclaim_task["credentials"]
 
 
 @pytest.mark.asyncio
-async def test_credentials_fd_closed_on_reset(rw_context, claim_task):
+async def test_credentials_file_closed_on_reset(rw_context, claim_task):
     rw_context.claim_task = claim_task
-    fd = rw_context.credentials_fd
+    fd = rw_context.credentials_file.fileno()
     rw_context.claim_task = None
-    assert rw_context.credentials_fd == -1
+    assert rw_context.credentials_file is None
     with pytest.raises(OSError):
         os.fstat(fd)