diff --git a/include/r3.h b/include/r3.h
index 58d1160..26a5352 100644
--- a/include/r3.h
+++ b/include/r3.h
@@ -12,14 +12,10 @@
 #include <string.h>
 #include <pcre.h>
 #include <stdbool.h>
-#include "config.h"
 #include "r3_define.h"
 #include "str_array.h"
 #include "match_entry.h"
 
-#ifdef ENABLE_JSON
-#include <json-c/json.h>
-#endif
 
 
 #ifdef __cplusplus
@@ -108,7 +104,7 @@ edge * r3_node_find_edge(const node * n, const char * pat, int pat_len);
 void r3_node_append_edge(node *n, edge *child);
 
 
-edge * r3_node_find_common_prefix(node *n, char *path, int path_len, int *prefix_len, char **errstr);
+edge * r3_node_find_common_prefix(node *n, const char *path, int path_len, int *prefix_len, char **errstr);
 
 node * r3_tree_insert_pathl(node *tree, const char *path, int path_len, void * data);
 
@@ -181,34 +177,6 @@ enum { NODE_COMPARE_STR, NODE_COMPARE_PCRE, NODE_COMPARE_OPCODE };
 
 enum { OP_EXPECT_MORE_DIGITS = 1, OP_EXPECT_MORE_WORDS, OP_EXPECT_NOSLASH, OP_EXPECT_NODASH, OP_EXPECT_MORE_ALPHA };
 
-#ifdef ENABLE_JSON
-json_object * r3_edge_to_json_object(const edge * e);
-json_object * r3_node_to_json_object(const node * n);
-json_object * r3_route_to_json_object(const route * r);
-
-const char * r3_node_to_json_string_ext(const node * n, int options);
-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
diff --git a/include/r3_gvc.h b/include/r3_gvc.h
new file mode 100644
index 0000000..334fab9
--- /dev/null
+++ b/include/r3_gvc.h
@@ -0,0 +1,23 @@
+/*
+ * 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>
+#include "r3.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/include/r3_json.h b/include/r3_json.h
new file mode 100644
index 0000000..8925e1d
--- /dev/null
+++ b/include/r3_json.h
@@ -0,0 +1,24 @@
+/*
+ * r3_json.h
+ * Copyright (C) 2014 c9s <c9s@c9smba.local>
+ *
+ * Distributed under terms of the MIT license.
+ */
+
+#ifndef R3_JSON_H
+#define R3_JSON_H
+
+#include <json-c/json.h>
+#include "r3.h"
+
+json_object * r3_edge_to_json_object(const edge * e);
+json_object * r3_node_to_json_object(const node * n);
+json_object * r3_route_to_json_object(const route * r);
+
+const char * r3_node_to_json_string_ext(const node * n, int options);
+const char * r3_node_to_json_pretty_string(const node * n);
+const char * r3_node_to_json_string(const node * n);
+
+
+
+#endif /* !R3_JSON_H */
diff --git a/src/edge.c b/src/edge.c
index ad6eb7f..ea4371e 100644
--- a/src/edge.c
+++ b/src/edge.c
@@ -4,6 +4,7 @@
  *
  * Distributed under terms of the MIT license.
  */
+#include "config.h"
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -17,8 +18,6 @@
 
 // Judy array
 // #include <Judy.h>
-#include <config.h>
-
 #include "r3.h"
 #include "r3_str.h"
 #include "slug.h"
diff --git a/src/gvc.c b/src/gvc.c
index 963df28..5475409 100644
--- a/src/gvc.c
+++ b/src/gvc.c
@@ -4,11 +4,12 @@
  *
  * Distributed under terms of the MIT license.
  */
-
+#include "config.h"
 #include <gvc.h>
 #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/src/json.c b/src/json.c
index a8a1194..61af5cb 100644
--- a/src/json.c
+++ b/src/json.c
@@ -4,10 +4,10 @@
  *
  * Distributed under terms of the MIT license.
  */
-#include <json-c/json.h>
 #include "config.h"
+#include <json-c/json.h>
 #include "r3.h"
-
+#include "r3_json.h"
 
 json_object * r3_route_to_json_object(const route * r) {
     json_object *obj;
diff --git a/src/node.c b/src/node.c
index 93d1f82..cafa643 100644
--- a/src/node.c
+++ b/src/node.c
@@ -494,7 +494,7 @@ node * r3_tree_insert_pathl(node *tree, const char *path, int path_len, void * d
  * 4.  "aaa{slug:xxx}/hate" vs "aab{slug:yyy}/bar"      => common prefix = "aa"
  * 5.  "/foo/{slug}/hate" vs "/fo{slug}/bar"            => common prefix = "/fo"
  */
-edge * r3_node_find_common_prefix(node *n, char *path, int path_len, int *prefix_len, char **errstr) {
+edge * r3_node_find_common_prefix(node *n, const char *path, int path_len, int *prefix_len, char **errstr) {
     int i = 0;
     int prefix = 0;
     *prefix_len = 0;
diff --git a/src/slug.c b/src/slug.c
index a55c2fe..4edbead 100644
--- a/src/slug.c
+++ b/src/slug.c
@@ -15,11 +15,11 @@
 
 
 
-r3_slug_t * r3_slug_new(char * path, int path_len) {
+r3_slug_t * r3_slug_new(const char * path, int path_len) {
     r3_slug_t * s = zmalloc(sizeof(r3_slug_t));
     if (!s)
         return NULL;
-    s->path = path;
+    s->path = (char*) path;
     s->path_len = path_len;
 
     s->begin = NULL;
@@ -76,8 +76,8 @@ Return 1 => Slug found
 Return -1 => Slug parsing error
 */
 
-int r3_slug_parse(r3_slug_t *s, char *needle, int needle_len, char *offset, char **errstr) {
-    s->path = needle;
+int r3_slug_parse(r3_slug_t *s, const char *needle, int needle_len, char *offset, char **errstr) {
+    s->path = (char*) needle;
     s->path_len = needle_len;
 
     if (offset == NULL) {
diff --git a/src/slug.h b/src/slug.h
index b42f6dd..cd51700 100644
--- a/src/slug.h
+++ b/src/slug.h
@@ -39,11 +39,11 @@ typedef struct {
 } r3_slug_t;
 
 
-r3_slug_t * r3_slug_new(char * path, int path_len);
+r3_slug_t * r3_slug_new(const char * path, int path_len);
 
 int r3_slug_check(r3_slug_t *s);
 
-int r3_slug_parse(r3_slug_t *s, char *needle, int needle_len, char *offset, char **errstr);
+int r3_slug_parse(r3_slug_t *s, const char *needle, int needle_len, char *offset, char **errstr);
 
 char * r3_slug_to_str(const r3_slug_t *s);
 
diff --git a/tests/check_gvc.c b/tests/check_gvc.c
index 6442d0a..b337f1d 100644
--- a/tests/check_gvc.c
+++ b/tests/check_gvc.c
@@ -9,6 +9,7 @@
 #include <check.h>
 #include <stdlib.h>
 #include "r3.h"
+#include "r3_gvc.h"
 #include "r3_str.h"
 #include "bench.h"
 
diff --git a/tests/check_json.c b/tests/check_json.c
index f15109e..fa8ec12 100644
--- a/tests/check_json.c
+++ b/tests/check_json.c
@@ -11,6 +11,7 @@
 #include <json-c/json.h>
 #include "r3.h"
 #include "r3_str.h"
+#include "r3_json.h"
 #include "zmalloc.h"
 
 START_TEST (test_json_encode)