diff --git a/package.json b/package.json
index 8cfd58853424fb91a52efbd7812af5268547a6d1..1f9ac4771431f664eb2fc71c08dff2d39956b158 100644
--- a/package.json
+++ b/package.json
@@ -4,9 +4,9 @@
     "description": "Build the static src.",
     "cacheDirectories": ["client/node_modules"],
     "scripts": {
-      "postinstall": "cd opentech/static_src && npm install && npm build:prod"
+      "postinstall": "cd opentech/static_src && yarn install && npm build:prod"
     },
     "engines": {
-        "node": ">=4"
+    "node": ">=7.0.0"
     }
 }