diff --git a/src/c/module.d b/src/c/module.d
index 84a588ba1..5e8101a27 100644
--- a/src/c/module.d
+++ b/src/c/module.d
@@ -183,4 +183,6 @@ free_modules(void)
   loop_across_stack_filo(var, ecl_core.modules) {
     ecl_del_module(var);
   } end_loop_across_stack();
+  ecl_free_stack(ecl_core.modules);
+  ecl_core.modules = ECL_NIL;
 }
diff --git a/src/c/process.d b/src/c/process.d
index f264a7afc..7260ed692 100644
--- a/src/c/process.d
+++ b/src/c/process.d
@@ -260,7 +260,12 @@ free_cpu_process(cl_env_ptr the_env)
 #ifdef ECL_WINDOWS_THREADS
   CloseHandle(the_env->thread);
 #endif
+#if 0
+  /* KLUDGE when we destroy the module in destroy_process, the stack is freed
+     and threads are dereferenced. It might be that GC will try to pick them up
+     to run finalizers -- in that case we will still require a process env. */
   ecl_set_process_env(NULL);
+#endif
   return ECL_NIL;
 }
 
@@ -276,6 +281,10 @@ free_env_process(cl_env_ptr the_env)
 static cl_object
 destroy_process(void)
 {
+#ifdef ECL_THREADS
+  ecl_free_stack(ecl_core.threads);
+  ecl_core.threads = ECL_NIL;
+#endif
   return ECL_NIL;
 }
 
diff --git a/src/c/stacks.d b/src/c/stacks.d
index 12b98b070..9d4c8a16d 100644
--- a/src/c/stacks.d
+++ b/src/c/stacks.d
@@ -1061,6 +1061,14 @@ ecl_stack_index(cl_object self) {
   return self->vector.fillp;
 }
 
+void
+ecl_wipe_stack(cl_object self) {
+  int i, fp=self->vector.fillp;
+  self->vector.fillp = 0;
+  for (i=0; i<fp; i++)
+    self->vector.self.t[i] = ECL_NIL;
+}
+
 cl_object
 ecl_stack_push(cl_object self, cl_object elt)
 {
diff --git a/src/h/external.h b/src/h/external.h
index b995d84a7..56c2a2d8a 100755
--- a/src/h/external.h
+++ b/src/h/external.h
@@ -307,6 +307,8 @@ extern ECL_API cl_index ecl_atomic_index_incf(cl_index *slot);
 
 /* stack.c */
 extern ECL_API cl_object ecl_make_stack(cl_index dim);
+extern ECL_API void ecl_free_stack(cl_object o);
+extern ECL_API void ecl_wipe_stack(cl_object o);
 extern ECL_API cl_object ecl_stack_push(cl_object stack, cl_object elt);
 extern ECL_API cl_object ecl_stack_del(cl_object stack, cl_object elt);
 extern ECL_API cl_object ecl_stack_popu(cl_object stack);