diff --git a/crates/kingfisher-rules/data/rules/testkube.yml b/crates/kingfisher-rules/data/rules/testkube.yml
index 49ddc88..a401bbb 100644
--- a/crates/kingfisher-rules/data/rules/testkube.yml
+++ b/crates/kingfisher-rules/data/rules/testkube.yml
@@ -5,7 +5,7 @@ rules:
       (?xi)
       \b
       (
-        tkcapi_[a-f0-9]{30,64}
+        tkcapi_[a-z0-9]{30,64}
       )
       \b
     pattern_requirements:
@@ -42,7 +42,7 @@ rules:
       (?xi)
       \b
       (
-        tkcorg_[a-f0-9]{16,32}
+        tkcorg_[a-z0-9]{16,32}
       )
       \b
     min_entropy: 3.0
@@ -59,7 +59,7 @@ rules:
       (?xi)
       \b
       (
-        tkcenv_[a-f0-9]{16,32}
+        tkcenv_[a-z0-9]{16,32}
       )
       \b
     min_entropy: 3.0