diff -up sage-5.8/spkg/build/sage-5.8/module_list.py.orig sage-5.8/spkg/build/sage-5.8/module_list.py --- sage-5.8/spkg/build/sage-5.8/module_list.py.orig 2013-03-19 15:53:00.047663124 -0300 +++ sage-5.8/spkg/build/sage-5.8/module_list.py 2013-03-19 15:53:10.095663509 -0300 @@ -1983,7 +1983,8 @@ ext_modules = [ # These extensions are to be compiled only if the # corresponding packages have been installed -from sage.misc.package import is_package_installed +def is_package_installed(name): + return False if is_package_installed('fes'): ext_modules.extend([