2 files changed, 8 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog
index 82b28fc1..8cae4f5d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-19  Kaz Kylheku  <kaz@kylheku.com>
+
+	* parser.c (parser_mark): Do not mark p->syntax_tree if
+	its value is nao. Introduced on 2015-06-10, "Error handling improvement
+	in read".
+
 2015-06-18  Kaz Kylheku  <kaz@kylheku.com>
 
 	* lib.c (mkstring): Fix neglect to null terminate.
diff --git a/parser.c b/parser.c
index 86511fdf..32052700 100644
--- a/parser.c
+++ b/parser.c
@@ -59,7 +59,8 @@ static void parser_mark(val obj)
   gc_mark(p->stream);
   gc_mark(p->name);
   gc_mark(p->prepared_msg);
-  gc_mark(p->syntax_tree);
+  if (p->syntax_tree != nao)
+    gc_mark(p->syntax_tree);
   gc_mark(p->primer);
 }