diff --git a/.woodpecker/.backend.yml b/.woodpecker/.backend.yml
index 3483c88..08ffcfc 100644
--- a/.woodpecker/.backend.yml
+++ b/.woodpecker/.backend.yml
@@ -1,6 +1,6 @@
 ---
 variables:
-  - &java_image "gradle:8.5.0-jdk21"
+  - &java_image "gradle:8.5.0-jdk21@sha256:d64047f74f0aefaae35916a3d29a2d8d5890bc4a5cc8f8d14f898c0afb5c8a16"
 when:
   path: "app/**"
   event: [push, tag]