diff --git a/letsencrypt/display/completer.py b/letsencrypt/display/completer.py
index 83dafa25d..fed476bb3 100644
--- a/letsencrypt/display/completer.py
+++ b/letsencrypt/display/completer.py
@@ -1,4 +1,4 @@
-"""Provides tab completion when prompting users for a path."""
+"""Provides Tab completion when prompting users for a path."""
 import glob
 # readline module is not available on all systems
 try:
@@ -8,9 +8,9 @@ except ImportError:
 
 
 class Completer(object):
-    """Provides tab completion when prompting users for a path.
+    """Provides Tab completion when prompting users for a path.
 
-    This class is meant to be used with readline to provide tab
+    This class is meant to be used with readline to provide Tab
     completion for users entering paths. The complete method can be
     passed to readline.set_completer directly, however, this function
     works best as a context manager. For example:
@@ -18,14 +18,14 @@ class Completer(object):
     with Completer():
         raw_input()
 
-    In this example, tab completion will be available during the call to
+    In this example, Tab completion will be available during the call to
     raw_input above, however, readline will be restored to its previous
     state when exiting the body of the with statement.
 
     """
 
     def __init__(self):
-        self._completer = self._delims = self._iter = None
+        self._iter = self._original_completer = self._original_delims = None
 
     def complete(self, text, state):
         """Provides path completion for use with readline.
@@ -43,8 +43,8 @@ class Completer(object):
         return next(self._iter, None)
 
     def __enter__(self):
-        self._completer = readline.get_completer()
-        self._delims = readline.get_completer_delims()
+        self._original_completer = readline.get_completer()
+        self._original_delims = readline.get_completer_delims()
 
         readline.set_completer(self.complete)
         readline.set_completer_delims(' \t\n;')
@@ -57,5 +57,5 @@ class Completer(object):
             readline.parse_and_bind('tab: complete')
 
     def __exit__(self, unused_type, unused_value, unused_traceback):
-        readline.set_completer_delims(self._delims)
-        readline.set_completer(self._completer)
+        readline.set_completer_delims(self._original_delims)
+        readline.set_completer(self._original_completer)
diff --git a/letsencrypt/display/util.py b/letsencrypt/display/util.py
index 005e2ba9c..20c6be156 100644
--- a/letsencrypt/display/util.py
+++ b/letsencrypt/display/util.py
@@ -13,7 +13,7 @@ WIDTH = 72
 HEIGHT = 20
 
 DSELECT_HELP = (
-    "Use the arrow keys or tab to move between window elements. Space can be "
+    "Use the arrow keys or Tab to move between window elements. Space can be "
     "used to complete the input path with the selected element in the "
     "directory window. Pressing enter will select the currently highlighted "
     "button.")
@@ -559,7 +559,9 @@ class NoninteractiveDisplay(object):
         """Simulate prompting the user for a directory.
 
         This function returns default if it is not ``None``, otherwise,
-        an exception is raised.
+        an exception is raised explaining the problem. If cli_flag is
+        not ``None``, the error message will include the flag that can
+        be used to set this value with the CLI.
 
         :param str message: prompt to give the user
         :param default: default value to return (if one exists)
diff --git a/letsencrypt/interfaces.py b/letsencrypt/interfaces.py
index 188a4d9da..2fba11869 100644
--- a/letsencrypt/interfaces.py
+++ b/letsencrypt/interfaces.py
@@ -449,7 +449,9 @@ class IDisplay(zope.interface.Interface):
         :param str message: prompt to give the user
         :param default: the default value to return, if one exists, when
             using the NoninteractiveDisplay
-        :param str cli_flag: option used to set this value with the CLI
+        :param str cli_flag: option used to set this value with the CLI,
+            if one exists, to be included in error messages given by
+            NoninteractiveDisplay
 
         :returns: tuple of the form (`code`, `string`) where
             `code` - int display exit code