diff --git a/.drone.yml b/.drone.yml
index 8b13cc4..1f810b5 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -23,7 +23,7 @@ steps:
       packer/windowsserver2019.json
   - |
     packer build \
-      -on-error=cleanup \
+      -on-error=cleanup -parallel-builds=1 \
       -var-file=packer/variables.vsphere.json \
       -var vm_name=$DRONE_BUILD_NUMBER-${DRONE_COMMIT_SHA:0:10} \
       -var vm_guestos=server2019 \