diff --git a/include/r3.h b/include/r3.h
index f3f689b..75c769a 100644
--- a/include/r3.h
+++ b/include/r3.h
@@ -148,7 +148,7 @@ route * r3_route_create(const char * path);
 
 route * r3_route_createl(const char * path, int path_len);
 
-int r3_route_cmp(route *r1, const match_entry *r2);
+int r3_route_cmp(const route *r1, const match_entry *r2);
 
 void r3_node_append_route(node * n, route * route);
 
@@ -166,7 +166,7 @@ route * r3_tree_match_route(const node *n, const match_entry * entry);
 
 
 
-int r3_pattern_to_opcode(char * pattern, int pattern_len);
+int r3_pattern_to_opcode(const char * pattern, int pattern_len);
 
 enum { NODE_COMPARE_STR, NODE_COMPARE_PCRE, NODE_COMPARE_OPCODE };
 
diff --git a/src/node.c b/src/node.c
index e6e48ec..b20b43a 100644
--- a/src/node.c
+++ b/src/node.c
@@ -640,7 +640,7 @@ void r3_tree_dump(const node * n, int level) {
  *
  * -1 == different route
  */
-int r3_route_cmp(route *r1, const match_entry *r2) {
+int r3_route_cmp(const route *r1, const match_entry *r2) {
     if (r1->request_method != 0) {
         if (0 == (r1->request_method & r2->request_method) ) {
             return -1;
diff --git a/src/str.c b/src/str.c
index 680a4f4..ffc3fe7 100644
--- a/src/str.c
+++ b/src/str.c
@@ -12,7 +12,7 @@
 #include "r3_str.h"
 #include "zmalloc.h"
 
-int r3_pattern_to_opcode(char * pattern, int len) {
+int r3_pattern_to_opcode(const char * pattern, int len) {
     if ( strncmp(pattern, "\\w+",len) == 0 ) {
         return OP_EXPECT_MORE_WORDS;
     }