Signtool returns error 0x800700C1 when signing the installer if the installerbase (maintenance tool) is signed

With the IFW 3.1.1 it is possible to sign the maintenance tool to get rid of the warning during uninstallation. But with a signed installerbase the Signtool returns the errorcode 0x800700C1  (ERROR_BAD_EXE_FORMAT) during signing the final installer binary.

It can be reproduced with the stylesheet example.

When the installerbase is not signed it is possible to sign the final installer binary.

installer_signed_installer_base.exe throws the error.

installer_unsigned_installer_base.exe can be signed.