diff --git a/host-runner.yaml b/host-runner.yaml
index ed9ef45..c94c415 100644
--- a/host-runner.yaml
+++ b/host-runner.yaml
@@ -11,7 +11,7 @@ runner:
   # Where to store the registration result.
   file: .runner
   # Execute how many tasks concurrently at the same time.
-  capacity: 20
+  capacity: 1
   # Extra environment variables to run jobs.
   envs:
   # Extra environment variables to run jobs from a file.