diff --git a/plugins/ssl/certificate_file_expiry b/plugins/ssl/certificate_file_expiry
index 0844092a..3485ce5f 100755
--- a/plugins/ssl/certificate_file_expiry
+++ b/plugins/ssl/certificate_file_expiry
@@ -72,6 +72,11 @@ if [ "$1" = "config" ] ; then
   echo "graph_category security"
 fi
 
+# by default when certificate is only valid for 5 days or less emit a warning
+warning=${warning:-5:}
+# by default when certificate is only valid for 1 day or less emit a critical
+critical=${critical:-1:}
+
 now=$(date +%s)
 for cert in ${CERTS}; do
   cert_type=${cert%:*}