diff --git a/nagios/check_whois b/nagios/check_whois
index d11d22f..78acc2f 100755
--- a/nagios/check_whois
+++ b/nagios/check_whois
@@ -110,7 +110,7 @@ extract_date_from_whois() {
 		)"
 
 	# Small protection against injection
-	if [ -n "$( echo "$EXPIRATION_DATE" | LANG=C sed -n '/^[a-zA-Z0-9:\-]\{1,64\}$/p' )" ]; then
+	if [ -n "$( echo "$EXPIRATION_DATE" | LANG=C sed -n '/^[a-zA-Z0-9:.\-]\{1,64\}$/p' )" ]; then
 		date --date="$EXPIRATION_DATE" +%s
 	fi
 }