diff --git a/pillar/application/__init__.py b/pillar/application/__init__.py
index 76366fee..1da7d02a 100644
--- a/pillar/application/__init__.py
+++ b/pillar/application/__init__.py
@@ -1,6 +1,6 @@
 import logging
 import os
-import json
+import tempfile
 from bson import ObjectId
 from datetime import datetime
 import bugsnag
@@ -101,7 +101,14 @@ if from_envvar:
     # configfile doesn't exist, it should error out (i.e. silent=False).
     app.config.from_pyfile(from_envvar, silent=False)
 
-# Set the TMP
+# Set the TMP environment variable to manage where uploads are stored.
+# These are all used by tempfile.mkstemp(), but we don't knwow in whic
+# order. As such, we remove all used variables but the one we set.
+tempfile.tempdir = app.config['STORAGE_DIR']
+os.environ['TMP'] = app.config['STORAGE_DIR']
+os.environ.pop('TEMP', None)
+os.environ.pop('TMPDIR', None)
+
 
 # Configure logging
 logging.basicConfig(
diff --git a/tests/test_file_storage.py b/tests/test_file_storage.py
new file mode 100644
index 00000000..decacd81
--- /dev/null
+++ b/tests/test_file_storage.py
@@ -0,0 +1,23 @@
+import os
+import tempfile
+
+from common_test_class import AbstractPillarTest
+
+
+class TempDirTest(AbstractPillarTest):
+    def test_tempfiles_location(self):
+        # After importing the application, tempfiles should be created in the STORAGE_DIR
+        storage = self.app.config['STORAGE_DIR']
+        self.assertEqual(os.environ['TMP'], storage)
+        self.assertNotIn('TEMP', os.environ)
+        self.assertNotIn('TMPDIR', os.environ)
+
+        handle, filename = tempfile.mkstemp()
+        os.close(handle)
+        dirname = os.path.dirname(filename)
+        self.assertEqual(dirname, storage)
+
+        tmpfile = tempfile.NamedTemporaryFile()
+        dirname = os.path.dirname(tmpfile.name)
+        self.assertEqual(dirname, storage)
+