diff --git a/src/musikbox/app/util/Duration.cpp b/src/musikbox/app/util/Duration.cpp
index f1b8de80c..2aaa364ad 100755
--- a/src/musikbox/app/util/Duration.cpp
+++ b/src/musikbox/app/util/Duration.cpp
@@ -49,7 +49,7 @@ namespace musik {
                 return Duration((int) round(seconds));
             }
 
-            std::string Duration(std::string& str) {
+            std::string Duration(const std::string& str) {
                 if (str.size()) {
                     int seconds = boost::lexical_cast<int>(str);
                     return Duration(seconds);
diff --git a/src/musikbox/app/util/Duration.h b/src/musikbox/app/util/Duration.h
index 30df47ece..79757674d 100755
--- a/src/musikbox/app/util/Duration.h
+++ b/src/musikbox/app/util/Duration.h
@@ -39,7 +39,7 @@
 namespace musik {
     namespace box {
         namespace duration {
-            std::string Duration(std::string& str);
+            std::string Duration(const std::string& str);
             std::string Duration(int seconds);
             std::string Duration(double seconds);
         }