diff --git a/acme.sh b/acme.sh
index b57228d3..0578e1ac 100755
--- a/acme.sh
+++ b/acme.sh
@@ -65,7 +65,7 @@ ID_TYPE_IP="ip"
 
 LOCAL_ANY_ADDRESS="0.0.0.0"
 
-DEFAULT_RENEW=30
+DEFAULT_RENEW="${DEFAULT_RENEW:-30}"
 
 NO_VALUE="no"