diff --git a/doc/integration/imap_and_smtp.rst b/doc/integration/imap_and_smtp.rst
index cfcd02ab4..be670a535 100644
--- a/doc/integration/imap_and_smtp.rst
+++ b/doc/integration/imap_and_smtp.rst
@@ -422,7 +422,7 @@ be used by Postfix to lookup into Modoboa tables.
 To automaticaly generate the requested map files and store them in a
 directory, run the following command::
 
-  $ modoboa-admin.py postfix_maps --dbtype <mysql|postgres|sqlite> --extensions <extension names> <directory>
+  $ modoboa-admin.py postfix_maps --dbtype <mysql|postgres|sqlite> --extensions all <directory>
 
 ``<directory>`` is the directory where the files will be
 stored. Answer the few questions and you're done.
diff --git a/modoboa/core/commands/postfix_maps.py b/modoboa/core/commands/postfix_maps.py
index f10c6e111..ddcbed991 100644
--- a/modoboa/core/commands/postfix_maps.py
+++ b/modoboa/core/commands/postfix_maps.py
@@ -11,6 +11,7 @@ from django.template import Context, Template
 
 import dj_database_url
 
+from modoboa.lib.api_client import ModoAPIClient
 from . import Command
 
 MAP_FILE_TEMPLATE = """user = {{ dbuser }}
@@ -85,8 +86,11 @@ class MapFilesGenerator(object):
         """Load specified extensions."""
         if "all" in extensions:
             # Retrieve extension list from the API
-            return
+            official_exts = ModoAPIClient().list_extensions()
+            extensions = [extension["name"] for extension in official_exts]
+
         for extension in extensions:
+            extension = extension.replace("-", "_")
             try:
                 __import__(extension, locals(), globals(), ["postfix_maps"])
             except ImportError:
@@ -126,6 +130,9 @@ query = {{ query|safe }}
 
 
 class PostfixMapsCommand(Command):
+
+    """Base command to generate map files."""
+
     help = "Generate ready-to-use postfix map files"
 
     def __init__(self, *args, **kwargs):