Index: /trunk/ccl/lisp-kernel/x86-exceptions.c
===================================================================
--- /trunk/ccl/lisp-kernel/x86-exceptions.c	(revision 5390)
+++ /trunk/ccl/lisp-kernel/x86-exceptions.c	(revision 5391)
@@ -1929,4 +1929,9 @@
   pseudosigcontext->uc_onstack = 0;
   pseudosigcontext->uc_sigmask = (sigset_t) 0;
+  pseudosigcontext->uc_stack.ss_sp = 0;
+  pseudosigcontext->uc_stack.ss_size = 0;
+  pseudosigcontext->uc_stack.ss_flags = 0;
+  pseudosigcontext->uc_link = NULL;
+  pseudosigcontext->uc_mcsize = sizeof(*UC_MCONTEXT(pseudosigcontext));
   tcr->pending_exception_context = pseudosigcontext;
   tcr->valence = TCR_STATE_EXCEPTION_WAIT;