diff --git a/docs/index.rst b/docs/index.rst
index 4a38989..ded86f2 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -157,10 +157,10 @@ After the extension is initialized, a ``db`` group will be added to the command-
 - ``flask db edit <revision>``
     Edit a revision script using $EDITOR.
 
-- ``flask db upgrade [--sql] [--tag TAG] [--x-arg ARG] <revision>``
+- ``flask db upgrade [--sql] [--tag TAG] <revision>``
     Upgrades the database. If ``revision`` isn't given then ``"head"`` is assumed.
     
-- ``flask db downgrade [--sql] [--tag TAG] [--x-arg ARG] <revision>``
+- ``flask db downgrade [--sql] [--tag TAG] <revision>``
     Downgrades the database. If ``revision`` isn't given then ``-1`` is assumed.
     
 - ``flask db stamp [--sql] [--tag TAG] <revision>``
@@ -186,7 +186,8 @@ After the extension is initialized, a ``db`` group will be added to the command-
 
 Notes:
  
-- All commands also take a ``--directory DIRECTORY`` option that points to the directory containing the migration scripts. If this argument is omitted the directory used is ``migrations``.
+- All commands take one or more ``--x-arg ARG=VALUE`` or ``-x ARG=VALUE`` options with custom arguments that can be used in ``env.py``.
+- All commands take a ``--directory DIRECTORY`` option that points to the directory containing the migration scripts. If this argument is omitted the directory used is ``migrations``.
 - The default directory can also be specified as a ``directory`` argument to the ``Migrate`` constructor.
 - The ``--sql`` option present in several commands performs an 'offline' mode migration. Instead of executing the database commands the SQL statements that need to be executed are printed to the console.
 - Detailed documentation on these commands can be found in the `Alembic's command reference page <http://alembic.zzzcomputing.com/en/latest/api/commands.html>`_.
diff --git a/src/flask_migrate/__init__.py b/src/flask_migrate/__init__.py
index c61b7f5..f0f9301 100644
--- a/src/flask_migrate/__init__.py
+++ b/src/flask_migrate/__init__.py
@@ -3,7 +3,7 @@
 import logging
 import os
 import sys
-from flask import current_app
+from flask import current_app, g
 from alembic import __version__ as __alembic_version__
 from alembic.config import Config as AlembicConfig
 from alembic import command
@@ -92,15 +92,15 @@ def get_config(self, directory=None, x_arg=None, opts=None):
         for opt in opts or []:
             setattr(config.cmd_opts, opt, True)
         if not hasattr(config.cmd_opts, 'x'):
+            setattr(config.cmd_opts, 'x', [])
+            for x in g.x_arg:
+                config.cmd_opts.x.append(x)
             if x_arg is not None:
-                setattr(config.cmd_opts, 'x', [])
                 if isinstance(x_arg, list) or isinstance(x_arg, tuple):
                     for x in x_arg:
                         config.cmd_opts.x.append(x)
                 else:
                     config.cmd_opts.x.append(x_arg)
-            else:
-                setattr(config.cmd_opts, 'x', None)
         return self.call_configure_callbacks(config)
 
 
diff --git a/src/flask_migrate/cli.py b/src/flask_migrate/cli.py
index 176672c..5bfd4b5 100644
--- a/src/flask_migrate/cli.py
+++ b/src/flask_migrate/cli.py
@@ -1,4 +1,5 @@
 import click
+from flask import g
 from flask.cli import with_appcontext
 from flask_migrate import list_templates as _list_templates
 from flask_migrate import init as _init
@@ -18,9 +19,12 @@
 
 
 @click.group()
-def db():
+@click.option('-x', '--x-arg', multiple=True,
+              help='Additional arguments consumed by custom env.py scripts')
+@with_appcontext
+def db(x_arg):
     """Perform database migrations."""
-    pass
+    g.x_arg = x_arg  # these will be picked up by Migrate.get_config()
 
 
 @db.command()