diff --git a/requirements.txt b/requirements.txt
index 39bdc4144..c5d14c624 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,3 @@
 amaranth-yosys==0.35.0.0.post81
 git+https://github.com/amaranth-lang/amaranth@94c504afc7d81738ecdc9523a2615ef43ecbf51a
+typing-extensions==4.9.0