diff --git a/coverage.sh b/coverage.sh
index dc670c8..f8e7a37 100755
--- a/coverage.sh
+++ b/coverage.sh
@@ -335,7 +335,7 @@ if [ $variant = - ]; then
 fi
 
 # check if the file content differs
-diff --unified --no-dereference --recursive /tmp/debian-$dist-debootstrap /tmp/debian-$dist-mm
+diff --unified --no-dereference --recursive /tmp/debian-$dist-debootstrap /tmp/debian-$dist-mm >&2
 
 # check permissions, ownership, symlink targets, modification times using tar
 # directory mtimes will differ, thus we equalize them first