diff --git a/util/config/provider/baseprovider.py b/util/config/provider/baseprovider.py
index 97360d309..d3bea873e 100644
--- a/util/config/provider/baseprovider.py
+++ b/util/config/provider/baseprovider.py
@@ -80,7 +80,7 @@ class BaseProvider(object):
     """ Returns whether the file with the given name exists under the config override volume. """
     raise NotImplementedError
 
-  def get_volume_file(self, filename):
+  def get_volume_file(self, filename, mode='r'):
     """ Returns a Python file referring to the given name under the config override volume. """
     raise NotImplementedError
 
diff --git a/util/config/provider/fileprovider.py b/util/config/provider/fileprovider.py
index 3462eb7e2..099c5c3fd 100644
--- a/util/config/provider/fileprovider.py
+++ b/util/config/provider/fileprovider.py
@@ -49,8 +49,8 @@ class FileConfigProvider(BaseProvider):
   def volume_file_exists(self, filename):
     return os.path.exists(os.path.join(self.config_volume, filename))
 
-  def get_volume_file(self, filename):
-    return open(os.path.join(self.config_volume, filename))
+  def get_volume_file(self, filename, mode='r'):
+    return open(os.path.join(self.config_volume, filename), mode=mode)
 
   def write_volume_file(self, filename, contents):
     filepath = os.path.join(self.config_volume, filename)