diff --git a/Dockerfile b/Dockerfile
index 1f32d04..5f878b3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -38,7 +38,7 @@ COPY proto proto
 RUN cargo install --locked --path . --root /build
 
 # run
-FROM debian:13-slim AS runtime
+FROM debian:13-slim@sha256:3a39a0592364683e6bab97937b72cad5a8fa6dcbbee90edb3bb48c7f8e94f258 AS runtime
 RUN apt-get update -y && apt-get upgrade -y && \
     apt-get install --no-install-recommends -y ca-certificates libssl-dev lsb-release && \
     rm -rf /var/lib/apt/lists/*