diff --git a/.github/workflows/preview.yml b/.github/workflows/preview.yml
index cfbde8e..3ceb1c9 100644
--- a/.github/workflows/preview.yml
+++ b/.github/workflows/preview.yml
@@ -7,7 +7,7 @@
 name: Update PDF Preview
 
 env:
-  doc_name:
+  doc_name: add missing env:doc_name
 
 on:
   push: