diff --git a/constraints-oldest.txt b/constraints-oldest.txt
index 010762f26..3bbc33a6e 100644
--- a/constraints-oldest.txt
+++ b/constraints-oldest.txt
@@ -6,6 +6,7 @@
 airium==0.2.3
 bandit==1.7.1
 black==21.8b0
+blue==0.8.0
 codespell==2.1.0
 defusedxml==0.7.1
 flake8-2020==1.6.1
diff --git a/setup.cfg b/setup.cfg
index 67894f47b..886316cd5 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -46,6 +46,8 @@ 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
     airium>=0.2.3