diff --git a/route.cc b/route.cc
index 45cdaa2..4e23225 100644
--- a/route.cc
+++ b/route.cc
@@ -4,21 +4,21 @@ namespace route {
 
   using namespace std;
 
-  Match Route::set(string u) {
+  Match Route::set(const string& u) {
     url = u;
     path_to_regex = regex(path_pattern); 
     Match m(*this);
     return m;
   }
 
-  string Match::get(string key) {
+  string Match::get(const string& key) {
     if (pairs.count(key)) {
       return pairs.at(key);
     }
     return "";
   }
 
-  bool Match::test(string tmpl) {
+  bool Match::test(const string& tmpl) {
 
     pairs.clear();
     Path path;
diff --git a/route.h b/route.h
index 31d4c03..5da4b0f 100644
--- a/route.h
+++ b/route.h
@@ -57,7 +57,7 @@ class Route {
     // set the url for this instance, create a regex
     // from the url and return a match instance.
     //
-    Match set(string u); 
+    Match set(const string& u); 
 
     Route(/* options */) {
       //
@@ -77,8 +77,8 @@ class Match {
 
   public:
     int keys;
-    string get(string key);
-    bool test(string tmpl);
+    string get(const string& key);
+    bool test(const string& tmpl);
 
     Match(Route &r) : route(&r) {}
     ~Match() {}