diff --git a/src/beanify/main.py b/src/beanify/main.py
index 7f5bf51..1d8ebe4 100644
--- a/src/beanify/main.py
+++ b/src/beanify/main.py
@@ -84,7 +84,7 @@ parser.add_argument(
 parser.add_argument(
     dest="ingest",
     help="File(s) to ingest (must be in the correct format for the selected converter).",
-    action="append",
+    nargs="*",
 )
 parser.add_argument(
     "--rules",
@@ -211,8 +211,9 @@ async def main():
         batch_mode_process(config, converter, ruleset, args.ingest)
     else:
         # GUI mode
+        theme = config["beanify"].get("theme") or "clam"
         window = MainWindow(
-            config, converter, ruleset, initial_files=args.ingest, theme="clam"
+            config, converter, ruleset, initial_files=args.ingest, theme=theme
         )
         window.mainloop()