diff --git a/Makefile.am b/Makefile.am
index 0d9861b..6e1b0e6 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -25,7 +25,6 @@ r3_include_HEADERS = \
 	include/r3_define.h \
 	include/r3_list.h \
 	include/r3_str.h \
-	include/r3_gvc.h \
 	include/str_array.h \
 	$(NULL)
 
diff --git a/README.md b/README.md
index 51ca996..0d67182 100644
--- a/README.md
+++ b/README.md
@@ -36,11 +36,13 @@ Pattern Syntax
     /blog/post/{id:\d+}  use `\d+` regular expression instead of default.
 
 
-C API
+API
 ------------------------
 
 ```c
 #include <r3.h>
+#include <r3_str.h>
+
 
 // create a router tree with 10 children capacity (this capacity can grow dynamically)
 n = r3_tree_create(10);
diff --git a/include/r3.h b/include/r3.h
index b75450b..58d1160 100644
--- a/include/r3.h
+++ b/include/r3.h
@@ -191,8 +191,29 @@ const char * r3_node_to_json_pretty_string(const node * n);
 const char * r3_node_to_json_string(const node * n);
 #endif
 
+
+#ifdef ENABLE_GRAPHVIZ
+#include <stdio.h>
+#include <gvc.h>
+
+void r3_tree_build_ag_nodes(Agraph_t * g, Agnode_t * ag_parent_node, const node * n, int node_cnt);
+
+int r3_tree_render(const node * tree, const char *layout, const char * format, FILE *fp);
+
+int r3_tree_render_dot(const node * tree, const char *layout, FILE *fp);
+
+int r3_tree_render_file(const node * tree, const char * format, const char * filename);
+#endif
+
+
+
+
+
 #ifdef __cplusplus
 }
 #endif
 
+
+
+
 #endif /* !R3_NODE_H */
diff --git a/include/r3_gvc.h b/include/r3_gvc.h
deleted file mode 100644
index 4d2b56f..0000000
--- a/include/r3_gvc.h
+++ /dev/null
@@ -1,21 +0,0 @@
-/*
- * r3_gvc.h
- * Copyright (C) 2014 c9s <c9s@c9smba.local>
- *
- * Distributed under terms of the MIT license.
- */
-#ifndef R3_GVC_H
-#define R3_GVC_H
-
-#include <stdio.h>
-#include <gvc.h>
-
-void r3_tree_build_ag_nodes(Agraph_t * g, Agnode_t * ag_parent_node, const node * n, int node_cnt);
-
-int r3_tree_render(const node * tree, const char *layout, const char * format, FILE *fp);
-
-int r3_tree_render_dot(const node * tree, const char *layout, FILE *fp);
-
-int r3_tree_render_file(const node * tree, const char * format, const char * filename);
-
-#endif /* !R3_GVC_H */
diff --git a/src/gvc.c b/src/gvc.c
index e24a555..963df28 100644
--- a/src/gvc.c
+++ b/src/gvc.c
@@ -9,7 +9,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include "r3.h"
-#include "r3_gvc.h"
 #include "zmalloc.h"
 
 void r3_tree_build_ag_nodes(Agraph_t * g, Agnode_t * ag_parent_node, const node * n, int node_cnt) {
diff --git a/tests/check_gvc.c b/tests/check_gvc.c
index ae43a60..6442d0a 100644
--- a/tests/check_gvc.c
+++ b/tests/check_gvc.c
@@ -10,7 +10,6 @@
 #include <stdlib.h>
 #include "r3.h"
 #include "r3_str.h"
-#include "r3_gvc.h"
 #include "bench.h"
 
 START_TEST (test_gvc_render_dot)