diff --git a/azure-pipelines-ci.yml b/azure-pipelines-ci.yml
index 02ac3c7f571..860d04d9c91 100644
--- a/azure-pipelines-ci.yml
+++ b/azure-pipelines-ci.yml
@@ -14,6 +14,7 @@ jobs:
   pool:
     vmImage: 'ubuntu-latest'
   strategy:
+    maxParallel: 1
     matrix:
       Python35:
         python.version: '3.5'