--- a/coverage.sh
+++ b/coverage.sh
@@ -203,10 +203,26 @@ for f in "/tmp/debian-$dist-debootstrap/
 done
 
 # workaround for https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=917773
-awk -v FS=: -v OFS=: -v SDE=\$SOURCE_DATE_EPOCH '{ print \$1,\$2,int(SDE/60/60/24),\$4,\$5,\$6,\$7,\$8,\$9 }' < /tmp/debian-$dist-mm/etc/shadow > /tmp/debian-$dist-mm/etc/shadow.bak
-mv /tmp/debian-$dist-mm/etc/shadow.bak /tmp/debian-$dist-mm/etc/shadow
-awk -v FS=: -v OFS=: -v SDE=\$SOURCE_DATE_EPOCH '{ print \$1,\$2,int(SDE/60/60/24),\$4,\$5,\$6,\$7,\$8,\$9 }' < /tmp/debian-$dist-mm/etc/shadow- > /tmp/debian-$dist-mm/etc/shadow-.bak
-mv /tmp/debian-$dist-mm/etc/shadow-.bak /tmp/debian-$dist-mm/etc/shadow-
+if ! cmp /tmp/debian-$dist-debootstrap/etc/shadow /tmp/debian-$dist-mm/etc/shadow; then
+	echo patching /etc/shadow on $dist $variant
+	head /tmp/debian-$dist-debootstrap/etc/shadow /tmp/debian-$dist-mm/etc/shadow
+	echo \$SOURCE_DATE_EPOCH
+	awk -v SDE=\$SOURCE_DATE_EPOCH 'BEGIN { print int(SDE/60/60/24) }'
+	awk -v FS=: -v OFS=: -v SDE=\$SOURCE_DATE_EPOCH '{ print \$1,\$2,int(SDE/60/60/24),\$4,\$5,\$6,\$7,\$8,\$9 }' < /tmp/debian-$dist-mm/etc/shadow > /tmp/debian-$dist-mm/etc/shadow.bak
+	mv /tmp/debian-$dist-mm/etc/shadow.bak /tmp/debian-$dist-mm/etc/shadow
+else
+	echo no difference for /etc/shadow on $dist $variant
+fi
+if ! cmp /tmp/debian-$dist-debootstrap/etc/shadow- /tmp/debian-$dist-mm/etc/shadow-; then
+	echo patching /etc/shadow- on $dist $variant
+	echo \$SOURCE_DATE_EPOCH
+	awk -v SDE=\$SOURCE_DATE_EPOCH 'BEGIN { print int(SDE/60/60/24) }'
+	head /tmp/debian-$dist-debootstrap/etc/shadow- /tmp/debian-$dist-mm/etc/shadow-
+	awk -v FS=: -v OFS=: -v SDE=\$SOURCE_DATE_EPOCH '{ print \$1,\$2,int(SDE/60/60/24),\$4,\$5,\$6,\$7,\$8,\$9 }' < /tmp/debian-$dist-mm/etc/shadow- > /tmp/debian-$dist-mm/etc/shadow-.bak
+	mv /tmp/debian-$dist-mm/etc/shadow-.bak /tmp/debian-$dist-mm/etc/shadow-
+else
+	echo no difference for /etc/shadow- on $dist $variant
+fi
 
 # check if the file content differs
 diff --no-dereference --recursive /tmp/debian-$dist-debootstrap /tmp/debian-$dist-mm
