Although the package does not include any shared libraries, it does have a shlibs control file. If you did include a shared library, check that the SONAME of the library is set and that it matches the contents of the shlibs file.
SONAMEs are set with something like gcc -Wl,-soname,libfoo.so.0, where 0 is the major version of the library. If your package uses libtool, then libtool invoked with the right options should be doing this.
Note this is sometimes triggered for packages with a private shared library due to a bug in Debhelper.