diff --git a/openpgp-card-sequoia/README.md b/openpgp-card-sequoia/README.md
index 28c7185..af9b26a 100644
--- a/openpgp-card-sequoia/README.md
+++ b/openpgp-card-sequoia/README.md
@@ -21,7 +21,7 @@ NOTE: data on this card will be deleted in the process of running this
 program!
 
 ```
-$ export TEST_CARD_SERIAL="01234567"
+$ export TEST_CARD_IDENT="0123:4567ABCD"
 $ cargo run
 ```