diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6f79fb7aa564a75be9df4f99a4b20e5930882272..77a26aaf0fcd92ed9ab511306249593ba1ede591 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -182,7 +182,7 @@ jobs:
             nix-build \
               --argstr hypothesisProfile ci \
               --arg collectCoverage true \
-              --arg tahoe-lafs << parameters.tahoe-version >> \
+              --argstr tahoe-lafs << parameters.tahoe-version >> \
               --attr doc
 
       - run: