diff --git a/guix-data-service/web/server.scm b/guix-data-service/web/server.scm
index eb3e601..080e747 100644
--- a/guix-data-service/web/server.scm
+++ b/guix-data-service/web/server.scm
@@ -351,5 +351,5 @@ port. Also, the port used can be changed by passing the --port option.\n"
 
           (wait finished?))
         #:hz 0
-        #:parallelism 4))
+        #:parallelism 1))
      finished?)))