diff --git a/bots/zmirror-renew-kerberos b/bots/zmirror-renew-kerberos
index d8fe998..efd4d0d 100755
--- a/bots/zmirror-renew-kerberos
+++ b/bots/zmirror-renew-kerberos
@@ -1,2 +1,3 @@
 #!/bin/sh
-env KRB5CCNAME=/tmp/krb5cc_1000.tmp kinit -k -t /home/zulip/tabbott.extra.keytab tabbott/extra@ATHENA.MIT.EDU; mv /tmp/krb5cc_1000.tmp /tmp/krb5cc_1000
+krb_user_id=1051
+env KRB5CCNAME=/tmp/krb5cc_"$krb_user_id".tmp kinit -k -t /home/zulip/tabbott.extra.keytab tabbott/extra@ATHENA.MIT.EDU; mv /tmp/krb5cc_"$krb_user_id".tmp /tmp/krb5cc_"$krb_user_id"