27 CFR 24.153: Strengthening bonds.

In any instance where the penal sum of the bond on file becomes insufficient, the principal shall either give a strengthening bond with the same surety to attain a sufficient penal sum or give a new bond covering the entire liability. Strengthening bonds will not be approved where any notation is made thereon which is intended, or which may be construed, as a release of any former bond, or as limiting the amount of either bond to less than its full penal sum. Strengthening bonds will show the current date of execution and the effective date.