diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2ddfaa9cf..b2c723289 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,7 +18,7 @@ jobs:
     - name: test
       run: |
         sudo apt-get -y install tcl8.5
-        ./runtest --verbose
+        ./runtest --clients 4 --verbose
     - name: cluster-test
       run: |
         ./runtest-cluster