diff --git a/authentic2_idp_ltpa/utils.py b/authentic2_idp_ltpa/utils.py
index 3396d74..2ca64c6 100644
--- a/authentic2_idp_ltpa/utils.py
+++ b/authentic2_idp_ltpa/utils.py
@@ -5,7 +5,7 @@ import base64
 def to_hex(l):
     h = hex(long(l))[2:-1]
     h = '0' * (8 - len(h)) + h
-    return h
+    return h.upper()
 
 def decode_secret(secret):
     if secret.startswith('b64:'):