diff --git a/11.0/apache/Dockerfile b/11.0/apache/Dockerfile
index 4fa051f..7c2e09c 100644
--- a/11.0/apache/Dockerfile
+++ b/11.0/apache/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-debian.template
 FROM php:7.1-apache
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/11.0/fpm-alpine/Dockerfile b/11.0/fpm-alpine/Dockerfile
index 198eba7..16c3720 100644
--- a/11.0/fpm-alpine/Dockerfile
+++ b/11.0/fpm-alpine/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-alpine.template
 FROM php:7.1-fpm-alpine
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/11.0/fpm/Dockerfile b/11.0/fpm/Dockerfile
index 512aca6..13584b6 100644
--- a/11.0/fpm/Dockerfile
+++ b/11.0/fpm/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-debian.template
 FROM php:7.1-fpm
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/12.0/apache/Dockerfile b/12.0/apache/Dockerfile
index 130d2c7..6f0439d 100644
--- a/12.0/apache/Dockerfile
+++ b/12.0/apache/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-debian.template
 FROM php:7.1-apache
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/12.0/fpm-alpine/Dockerfile b/12.0/fpm-alpine/Dockerfile
index 9a76cac..928cf25 100644
--- a/12.0/fpm-alpine/Dockerfile
+++ b/12.0/fpm-alpine/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-alpine.template
 FROM php:7.1-fpm-alpine
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/12.0/fpm/Dockerfile b/12.0/fpm/Dockerfile
index 26dee8d..6483bed 100644
--- a/12.0/fpm/Dockerfile
+++ b/12.0/fpm/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-debian.template
 FROM php:7.1-fpm
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/13.0/apache/Dockerfile b/13.0/apache/Dockerfile
index 8e2b203..61a4c34 100644
--- a/13.0/apache/Dockerfile
+++ b/13.0/apache/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-debian.template
 FROM php:7.1-apache
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/13.0/fpm-alpine/Dockerfile b/13.0/fpm-alpine/Dockerfile
index 828be93..bd28f49 100644
--- a/13.0/fpm-alpine/Dockerfile
+++ b/13.0/fpm-alpine/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-alpine.template
 FROM php:7.1-fpm-alpine
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/13.0/fpm/Dockerfile b/13.0/fpm/Dockerfile
index d073380..ac61eed 100644
--- a/13.0/fpm/Dockerfile
+++ b/13.0/fpm/Dockerfile
@@ -1,3 +1,4 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-debian.template
 FROM php:7.1-fpm
 
 # entrypoint.sh and cron.sh dependencies
diff --git a/update.sh b/update.sh
index 7b5dbdf..aa3805a 100755
--- a/update.sh
+++ b/update.sh
@@ -55,7 +55,10 @@ function create_variant() {
 	# Create the version+variant directory with a Dockerfile.
 	mkdir -p "$dir"
 
-	cp "Dockerfile-${base[$variant]}.template" "$dir/Dockerfile"
+        template="Dockerfile-${base[$variant]}.template"
+        rm -f "$dir/Dockerfile"
+        echo "# DO NOT EDIT: created by update.sh from $template" > "$dir/Dockerfile"
+	cat "$template" >> "$dir/Dockerfile"
 
 	echo "updating $fullversion [$1] $variant"
 
@@ -71,6 +74,8 @@ function create_variant() {
 		s/%%MEMCACHED_VERSION%%/'"${pecl_versions[memcached]}"'/g;
 		s/%%REDIS_VERSION%%/'"${pecl_versions[redis]}"'/g;
 	' "$dir/Dockerfile"
+        # remove write permission as a reminder this file must be modified with this script
+        chmod -w "$dir/Dockerfile"
 
 	# Copy the shell scripts
 	for name in entrypoint cron; do