diff --git a/build.sh b/build.sh
index be6c909..2b5b715 100755
--- a/build.sh
+++ b/build.sh
@@ -3,6 +3,27 @@ VERSION=`xpath -q -e 'string(//PLUGIN/@version)' zabbix_agent.plg`
 FILE="zabbix_agent-$VERSION.package.tgz"
 echo "Version in plugin file: $VERSION"
 echo "Generated file will be: $FILE"
+
+if [ -e "$FILE" ]; then
+	echo "File already exists."
+	
+	givenMD5=`xpath -q -e 'string(//PLUGIN/@packageMD5)' zabbix_agent.plg`
+	read currentMD5 _ < <(md5sum "$FILE")
+	
+	if [ "$givenMD5" = "$currentMD5" ]; then
+		echo "MD5 value matches."
+	else
+		echo "MD5 value does not match!"
+		echo "unraid_zabbix.plg: $givenMD5"
+		echo "$FILE: $currentMD5"
+	fi
+	
+	if [ "$1" != "--force" ]; then
+		echo "Stopping now. Call '$0 --force' to force recreating the file."
+		exit 1
+	fi
+fi
+
 echo "Is this correct? If yes, press Enter. If not, press Ctrl-C."
 read
 
@@ -12,3 +33,4 @@ tar -czvf "$FILE" files
 echo
 read md5 _ < <(md5sum "$FILE")
 echo "MD5 of the resulting file for the plugin file: $md5"
+echo "Run this tool again to validate the MD5 value from the plugin file."