diff --git a/simple_backup/simple_backup.py b/simple_backup/simple_backup.py
index 750e5bc..6b2f5f2 100755
--- a/simple_backup/simple_backup.py
+++ b/simple_backup/simple_backup.py
@@ -679,7 +679,10 @@ def _read_config(config_file, user=None):
                    'numeric_ids': False}
 
     if not os.path.isfile(config_file):
-        logger.warning('Config file %s does not exist', config_file)
+        if user is not None:
+            logger.warning('Config file %s does not exist', config_file)
+        else:
+            logger.warning('User not specified. Can\'t read configuration file')
 
         return config_args
 
@@ -793,7 +796,12 @@ def simple_backup():
 
         if euid == 0:
             user = os.getenv('SUDO_USER')
-            homedir = os.path.expanduser(f'~{user}')
+
+            if user is not None:
+                homedir = os.path.expanduser(f'~{user}')
+            else:
+                logger.warning('Failed to detect user. You can use -u/--user parameter to manually specify it')
+                homedir = None
         else:
             user = os.getenv('USER')
             homedir = os.getenv('HOME')