diff --git a/requirements-test.txt b/requirements-test.txt
index 567b990cb..6db42c79b 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -13,3 +13,7 @@ pyfaidx==0.8.1.3
 # See https://nvidia.slack.com/archives/C02A7LYGHK8/p1734727482697309
 pytorch-lightning<2.5.0
 lightning<2.5.0
+
+# Temporary cdifflib pin, see
+# https://github.com/mduggan/cdifflib/issues/13
+cdifflib<=1.2.6