diff --git a/requirements.txt b/requirements.txt
index 25ad93b..216fec8 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,6 @@
 Flask>=3.1.3,<4
 gunicorn>=26.0
-castle>=7.1.0,<8
+# Test against the tagged 7.2.0 release before it lands on PyPI.
+# Once published, switch back to the registry version: castle>=7.2.0,<8
+castle @ git+https://github.com/castle/castle-python.git@v7.2.0
 python-dotenv>=1.2