diff --git a/constraints-future.txt b/constraints-future.txt
index c0dcf8ae1..6c3d500e7 100644
--- a/constraints-future.txt
+++ b/constraints-future.txt
@@ -4,5 +4,6 @@
 # up-to-date by adding entries for any packages we want to get early
 # incompatibility warnings for.
 black @ git+https://github.com/psf/black.git@main
+darkgraylib @ git+https://github.com/akaihola/darkgraylib.git@main
 flynt @ git+https://github.com/ikamensh/flynt.git@master
 isort @ git+https://github.com/PyCQA/isort.git@main