diff --git a/newsfragments/3326.minor b/newsfragments/3326.minor
new file mode 100644
index 000000000..e69de29bb
diff --git a/setup.cfg b/setup.cfg
index c2d224225..f4539279e 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -7,6 +7,8 @@ bdist_egg = update_version bdist_egg
 bdist_wheel = update_version bdist_wheel
 
 [flake8]
-# For now, only use pyflakes errors; flake8 is still helpful because it allows
-# ignoring specific errors/warnings when needed.
-select = F
\ No newline at end of file
+# Enforce all pyflakes constraints, and also prohibit tabs for indentation.
+# Reference:
+#   https://flake8.pycqa.org/en/latest/user/error-codes.html
+#   https://pycodestyle.pycqa.org/en/latest/intro.html#error-codes
+select = F, W191