diff --git a/content/en/cosign/signing/signing_with_containers.md b/content/en/cosign/signing/signing_with_containers.md
index 5bda009b..505a1479 100644
--- a/content/en/cosign/signing/signing_with_containers.md
+++ b/content/en/cosign/signing/signing_with_containers.md
@@ -18,7 +18,7 @@ $ cosign sign $IMAGE
 To create a test image to sign using [ttl.sh](https://ttl.sh), run the following commands:
 
 ```
-$ IMAGE_NAME=$(uuidgen)
+$ IMAGE_NAME=$(uuidgen | tr '[:upper:]' '[:lower:]')
 $ IMAGE=ttl.sh/$IMAGE_NAME:1h
 $ cosign copy alpine $IMAGE
 ```