diff --git a/checker/run-checker b/checker/run-checker
index 21e737d..dc236dd 100755
--- a/checker/run-checker
+++ b/checker/run-checker
@@ -144,7 +144,7 @@ do
 	[ -f $DET_TAGS/$tagname ] || touch $DET_TAGS/$tagname
 	oldsha=$(cat $DET_TAGS/$tagname)
 	newsha=$(git --git-dir $repodir show-ref --tags $tagname | cut -d' ' -f1)
-	if ! [ "$oldsha" = "$newsha" ] 
+	if ! [ "x$oldsha" = "x$newsha" ] 
 	then
 		# TAG_HASH = $newsha
 		# TAG_NAME = $tagname