diff --git a/src/eval.c b/src/eval.c
index 0326a828a81..921a7533a60 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3242,6 +3242,25 @@ If NFRAMES is more than the number of frames, the value is nil.  */)
 }
 
 
+void
+mark_backtrace ()
+{
+  register struct backtrace *backlist;
+  register int i;
+
+  for (backlist = backtrace_list; backlist; backlist = backlist->next)
+    {
+      mark_object (*backlist->function);
+
+      if (backlist->nargs == UNEVALLED || backlist->nargs == MANY)
+	i = 0;
+      else
+	i = backlist->nargs - 1;
+      for (; i >= 0; i--)
+	mark_object (backlist->args[i]);
+    }
+}
+
 void
 syms_of_eval ()
 {