diff --git a/examples/deepzoom/deepzoom_multiserver.py b/examples/deepzoom/deepzoom_multiserver.py
index 82b4734a..3869f3bb 100755
--- a/examples/deepzoom/deepzoom_multiserver.py
+++ b/examples/deepzoom/deepzoom_multiserver.py
@@ -356,8 +356,8 @@ def __init__(self, relpath: str):
     parser.add_argument(
         '-f',
         '--format',
-        metavar='{jpeg|png}',
         dest='DEEPZOOM_FORMAT',
+        choices=['jpeg', 'png'],
         help='image format for tiles [jpeg]',
     )
     parser.add_argument(
diff --git a/examples/deepzoom/deepzoom_server.py b/examples/deepzoom/deepzoom_server.py
index 1512460f..555997db 100755
--- a/examples/deepzoom/deepzoom_server.py
+++ b/examples/deepzoom/deepzoom_server.py
@@ -293,8 +293,8 @@ def xfrm(img: Image.Image) -> None:
     parser.add_argument(
         '-f',
         '--format',
-        metavar='{jpeg|png}',
         dest='DEEPZOOM_FORMAT',
+        choices=['jpeg', 'png'],
         help='image format for tiles [jpeg]',
     )
     parser.add_argument(
diff --git a/examples/deepzoom/deepzoom_tile.py b/examples/deepzoom/deepzoom_tile.py
index 211b9111..46d3b542 100755
--- a/examples/deepzoom/deepzoom_tile.py
+++ b/examples/deepzoom/deepzoom_tile.py
@@ -426,9 +426,9 @@ def _shutdown(self) -> None:
     parser.add_argument(
         '-f',
         '--format',
-        metavar='{jpeg|png}',
         dest='format',
         default='jpeg',
+        choices=['jpeg', 'png'],
         help='image format for tiles [jpeg]',
     )
     parser.add_argument(