http.client tunnel headers with None now crash
Passing None as a header value to http.client tunnel raises AttributeError in Python 3.14 and 3.15 instead of working
Tier II · Emerging Problems that are still building up.
3 public reports · first reported 10 October 2026 · last reported 11 October 2026
What's going wrong
After Python 3.14 and 3.15, calling the HTTPS tunnel setup in http.client with a None header value raises an AttributeError during connect, where earlier versions quietly accepted it.
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In the idea report
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