diff --git a/constraints-oldest.txt b/constraints-oldest.txt
index 4d5bcbaad..cc652f714 100644
--- a/constraints-oldest.txt
+++ b/constraints-oldest.txt
@@ -5,6 +5,7 @@
 # versions in `setup.cfg`.
 bandit==1.7.1
 black==21.8b0
+blue==0.8.0
 codespell==2.1.0
 flake8-2020==1.6.1
 flake8-bugbear==22.1.11
diff --git a/setup.cfg b/setup.cfg
index f004f6f84..a17b1bcd8 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -48,6 +48,8 @@ pygments.lexers =
 [options.extras_require]
 isort =
     isort>=5.0.1
+blue =
+    blue>=0.8.0
 test =
     # NOTE: remember to keep `constraints-oldest.txt` in sync with these
     bandit>=1.7.1