diff --git a/requirements_dev.txt b/requirements_dev.txt
index 81691b99..c4192524 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -42,7 +42,7 @@ sphinx-book-theme
 sphinx-gallery
 sphinx-pydantic
 sphinx_rtd_theme
-thewalrus==0.21.0
+thewalrus==0.20.0
 tox
 twine
 watchdog
diff --git a/setup.py b/setup.py
index c7ff11c5..42eafa1d 100644
--- a/setup.py
+++ b/setup.py
@@ -26,7 +26,7 @@
     "qutip==4.7.2",
     "sky130==0.7.1",
     "sax==0.8.8",  # Pinned for pydantic <v2 compatibility.
-    "thewalrus==0.21.0",
+    "thewalrus==0.20.0",
 ]
 
 test_requirements = [