2 files changed, 6 insertions, 6 deletions
diff --git a/node.c b/node.c
index dfbfc9eb44..4254fd7425 100644
--- a/node.c
+++ b/node.c
@@ -132,11 +132,11 @@ dump_option(VALUE buf, VALUE indent, VALUE opt)
     rb_hash_foreach(opt, add_option_i, (VALUE)&arg);
 }
 
-static void dump_node(VALUE, VALUE, int, NODE *);
+static void dump_node(VALUE, VALUE, int, const NODE *);
 static const char default_indent[] = "|   ";
 
 static void
-dump_array(VALUE buf, VALUE indent, int comment, NODE *node)
+dump_array(VALUE buf, VALUE indent, int comment, const NODE *node)
 {
     int field_flag;
     const char *next_indent = default_indent;
@@ -151,7 +151,7 @@ dump_array(VALUE buf, VALUE indent, int comment, NODE *node)
 }
 
 static void
-dump_node(VALUE buf, VALUE indent, int comment, NODE *node)
+dump_node(VALUE buf, VALUE indent, int comment, const NODE * node)
 {
     int field_flag;
     int i;
@@ -1056,7 +1056,7 @@ dump_node(VALUE buf, VALUE indent, int comment, NODE *node)
 }
 
 VALUE
-rb_parser_dump_tree(NODE *node, int comment)
+rb_parser_dump_tree(const NODE *node, int comment)
 {
     VALUE buf = rb_str_new_cstr(
 	"###########################################################\n"
diff --git a/node.h b/node.h
index 12f4d423a8..aa16a1f93f 100644
--- a/node.h
+++ b/node.h
@@ -470,7 +470,7 @@ typedef struct node_buffer_struct node_buffer_t;
 typedef struct rb_ast_struct {
     VALUE flags;
     VALUE reserved1;
-    NODE *root;
+    const NODE *root;
     node_buffer_t *node_buffer;
     VALUE mark_ary;
 } rb_ast_t;
@@ -488,7 +488,7 @@ VALUE rb_parser_end_seen_p(VALUE);
 VALUE rb_parser_encoding(VALUE);
 VALUE rb_parser_get_yydebug(VALUE);
 VALUE rb_parser_set_yydebug(VALUE, VALUE);
-VALUE rb_parser_dump_tree(NODE *node, int comment);
+VALUE rb_parser_dump_tree(const NODE *node, int comment);
 void rb_parser_set_options(VALUE, int, int, int, int);
 
 rb_ast_t *rb_parser_compile_cstr(VALUE, const char*, const char*, int, int);