diff --git a/integration_tests/dockerfiles/Dockerfile_test_workdir b/integration_tests/dockerfiles/Dockerfile_test_workdir
index 6c89e4c11..beb508d2b 100644
--- a/integration_tests/dockerfiles/Dockerfile_test_workdir
+++ b/integration_tests/dockerfiles/Dockerfile_test_workdir
@@ -1,4 +1,4 @@
-FROM gcr.io/google-appengine/debian9:latest
+FROM gcr.io/google-appengine/debian9@sha256:6b3aa04751aa2ac3b0c7be4ee71148b66d693ad212ce6d3244bd2a2a147f314a
 COPY context/foo foo
 WORKDIR /test
 # Test that this will be appended on to the previous command, to create /test/workdir