diff --git a/ci/test_imagefile b/ci/test_imagefile
index 224141b138f..f9cf3187a25 100644
--- a/ci/test_imagefile
+++ b/ci/test_imagefile
@@ -4,7 +4,8 @@
 
 # See ci/README.md for usage.
 
-ARG CI_IMAGE_NAME_TAG
+# We never want scratch, but default arg silences a Warning
+ARG CI_IMAGE_NAME_TAG=scratch
 FROM ${CI_IMAGE_NAME_TAG}
 
 ARG FILE_ENV