diff --git a/.travis.yml b/.travis.yml
index 9144cf7..c81844d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,9 @@ cache:
     - api/node_modules
     - web/node_modules
 
+environment:
+  CHILD_CONCURRENCY: 1
+
 script:
   - ./script/unittestweb
   - ./script/unittestapi