diff --git a/.flake8 b/.flake8
index 3f907841f..1378ecef4 100644
--- a/.flake8
+++ b/.flake8
@@ -1,6 +1,7 @@
 [flake8]
 max-line-length = 99
 indent-width = 4
+extend-ignore = E203
 include =
   setup.py
   src/pygambit
diff --git a/build_support/catalog/test_update.py b/build_support/catalog/test_update.py
index 2e0e402ad..1ee941b6c 100644
--- a/build_support/catalog/test_update.py
+++ b/build_support/catalog/test_update.py
@@ -695,7 +695,7 @@ def test_second_level_dropdown_is_not_open(self, tmp_path, monkeypatch):
         assert "   .. dropdown:: My Source\n   \n" in rst
         # Confirm :open: does not immediately follow the second-level dropdown
         src_idx = rst.index("   .. dropdown:: My Source")
-        assert ":open:" not in rst[src_idx:src_idx + 40]
+        assert ":open:" not in rst[src_idx : src_idx + 40]
 
     def test_game_dropdown_is_open(self, tmp_path, monkeypatch):
         """Individual game dropdowns carry ``:open:`` so game content is visible on expand."""
diff --git a/pyproject.toml b/pyproject.toml
index f7a60e8e4..c318f952a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -76,7 +76,7 @@ select = [
     "Q", # prefer double quotes
     "W291", # trailing-whitespace
 ]
-ignore = []
+ignore = ["E203"]
 
 fixable = ["ALL"]
 unfixable = []