diff --git a/requirements-testing.txt b/requirements-testing.txt
index 166756e..6efa092 100644
--- a/requirements-testing.txt
+++ b/requirements-testing.txt
@@ -7,7 +7,7 @@ pytest-xdist == 3.8.*
 types-PyYAML ~= 6.0
 # Pinned to 25.x because black 26+ produces different formatting output
 # that is incompatible with black 25 (last version supporting Python 3.9).
-black == 25.11.*
+black == 25.12.*
 ruff == 0.15.*
 mypy == 2.2.*; python_version >= "3.10"
 mypy == 1.19.*; python_version < "3.10"