diff --git a/.circleci/config.yml b/.circleci/config.yml
index d8e51b54ea62a29752e2e728f91db58da1424729..67c8ded0d41c91915f0a94d5b4d69303e1c498da 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -240,7 +240,7 @@ workflows:
         matrix:
           parameters:
             py-version:
-            - "3.9"
+            - "39"
             tahoe-lafs-source:
             - "tahoe-lafs"