diff --git a/disk-deactivate/disk-deactivate.jq b/disk-deactivate/disk-deactivate.jq
index 54d98f7..49508b8 100644
--- a/disk-deactivate/disk-deactivate.jq
+++ b/disk-deactivate/disk-deactivate.jq
@@ -54,7 +54,7 @@ def deactivate:
 
 def walk:
   [
-    (.mountpoints[] | "umount -R \(.)"),
+    (.mountpoints[] | select(. != null) | "umount -R \(.)"),
     ((.children // []) | map(walk)),
     remove,
     deactivate