diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 78bf9af..0cb14a8 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -17,7 +17,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         python -m pip install .[dev,cli]
-        python -m pip install opencv-python-headless>=4.8
+        python -m pip install 'opencv-python-headless>=4.8,<4.9'
     - name: Lint
       run: |
         make lint
diff --git a/april_vision/cli/marker_generator/marker_modes/mode_single.py b/april_vision/cli/marker_generator/marker_modes/mode_single.py
index 0a4c980..4b07172 100644
--- a/april_vision/cli/marker_generator/marker_modes/mode_single.py
+++ b/april_vision/cli/marker_generator/marker_modes/mode_single.py
@@ -1,5 +1,6 @@
 import argparse
 import logging
+from typing import Union
 
 from PIL import Image
 
@@ -21,6 +22,7 @@ def main(args: argparse.Namespace) -> None:
 
     marker_ids = parse_marker_ranges(tag_data, args.range)
 
+    page_size: Union[PageSize, CustomPageSize]
     if args.page_size == 'CROPPED':
         # Allow for an additional marker pixel border
         required_width = args.marker_size * (12 / 8)
diff --git a/april_vision/cli/marker_generator/utils.py b/april_vision/cli/marker_generator/utils.py
index 52dec4f..0eef21f 100644
--- a/april_vision/cli/marker_generator/utils.py
+++ b/april_vision/cli/marker_generator/utils.py
@@ -2,7 +2,7 @@
 from enum import Enum
 from typing import List, Tuple
 
-from font_roboto import Roboto  # type: ignore[import]
+from font_roboto import Roboto  # type: ignore[import,unused-ignore]
 
 from april_vision.cli.utils import ApriltagFamily, parse_ranges