I just upgraded from libc6 2.7-8 to 2.7-9. The upgrade breaks both SBCL 0.9.16 package (which hangs on dpkg-reconfigure) dpavlov-deb64:~# dpkg-reconfigure sbcl /usr/lib/common-lisp/bin/sbcl.sh loading and dumping clc. and SBCL 1.0.14 (which gives an error message) dpavlov-deb64:~# dpkg-reconfigure sbcl /usr/lib/common-lisp/bin/sbcl.sh loading and dumping clc. fatal error encountered in SBCL pid 4908(tid 47361548078800): GC invariant lost, file "gencgc.c", line 833 Welcome to LDB, a low-level debugger for the Lisp runtime environment. ldb> My system is Debian unstable, running on amd64. Hope that helps. Regards, Dmitry