diff --git a/tests/fixtures/complexity/Dockerfile/Dockerfile b/tests/fixtures/complexity/Dockerfile/Dockerfile
index 985fd1488..43eede361 100644
--- a/tests/fixtures/complexity/Dockerfile/Dockerfile
+++ b/tests/fixtures/complexity/Dockerfile/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:3.20 AS base
+FROM alpine:3.20@sha256:d9e853e87e55526f6b2917df91a2115c36dd7c696a35be12163d44e6e2a4b6bc AS base
 ENV TZ=UTC
 FROM base
 ENV APP_HOME=/app \
diff --git a/tests/fixtures/complexity/Dockerfile/Dockerfile.worker b/tests/fixtures/complexity/Dockerfile/Dockerfile.worker
index 35c273d65..27b168aac 100644
--- a/tests/fixtures/complexity/Dockerfile/Dockerfile.worker
+++ b/tests/fixtures/complexity/Dockerfile/Dockerfile.worker
@@ -1,4 +1,4 @@
-FROM alpine:3.20
+FROM alpine:3.20@sha256:d9e853e87e55526f6b2917df91a2115c36dd7c696a35be12163d44e6e2a4b6bc
 ENV APP_MODE=worker
 COPY run.sh /usr/local/bin/run.sh
 CMD ["/usr/local/bin/run.sh"]