diff --git a/.gitea/workflows/build-image.yaml b/.gitea/workflows/build-image.yaml
index 15bb70b..c6794c1 100644
--- a/.gitea/workflows/build-image.yaml
+++ b/.gitea/workflows/build-image.yaml
@@ -5,7 +5,8 @@ on:
     branches:
       - main
   schedule:
-    - cron: '5 4 * * *'
+    # every three of the month, at 04:05
+    - cron: '5 4 3 * *'