diff --git a/src/httpaste/__main__.py b/src/httpaste/__main__.py
index 4a6aae4..436a46c 100644
--- a/src/httpaste/__main__.py
+++ b/src/httpaste/__main__.py
@@ -30,7 +30,14 @@ def command_standalone(**kwargs):
     """
 
     from httpaste import load_config, get_flask_app
-    from gevent.pywsgi import WSGIServer
+
+    try:
+        from gevent.pywsgi import WSGIServer
+    except ImportError as e:
+        raise ImportError(' '.join((
+            'gevent is currently not installed.',
+            'Please install it by running \'python3 -m pip install gevent\'.'
+        ))) from e
 
     config, server_config = load_config(kwargs.get('config_path'))
 
@@ -110,7 +117,7 @@ def parser():
 
     p = argparse.ArgumentParser(description='Process some integers.')
 
-    sp = p.add_subparsers(dest='command')
+    sp = p.add_subparsers(dest='command', required=True)
 
     p_standalone = sp.add_parser('standalone', help=command_standalone.__doc__)
     p_standalone.add_argument('--config-path', '-c', required=True)