diff --git a/package.json b/package.json
index 9076b111..1f22f960 100644
--- a/package.json
+++ b/package.json
@@ -59,7 +59,9 @@
   },
   "optionalDependencies": {
     "elevator": "^2.1.0",
-    "removedrive": "^1.1.1"
+    "removedrive": "^1.1.1",
+    "spawn-sync": "^1.0.15",
+    "try-thread-sleep": "^1.0.2"
   },
   "dependencies": {
     "angular": "1.6.3",