diff --git a/README.md b/README.md
index 7219856..2d146fa 100644
--- a/README.md
+++ b/README.md
@@ -16,9 +16,11 @@ let myCert = new Cert({
     gitOriginRepo: "git@githhub.com/someuser/somereopo" // good for persistence in highly volatile environments like docker
 });
 
-myCert.getDomainCert("example.com");
+myCert.getDomainCert("example.com"); // returns promise
 ```
 
+> **Note:** cert supports async parallel cert fetching. If called twice for the same domain, only the first one will trigger.
+
 ## sslDir
 to use the certificates it is important to understand what the structure of the ssl directory looks like.