diff --git a/daemon/src/sip/siptransport.cpp b/daemon/src/sip/siptransport.cpp
index 7765a81b8b987d20724c5f2de6429fe83479fb60..34ebdd518045c406356e124fe264d14a5367581c 100644
--- a/daemon/src/sip/siptransport.cpp
+++ b/daemon/src/sip/siptransport.cpp
@@ -453,13 +453,14 @@ SipTransport::createUdpTransport(const std::string &interface, unsigned int port
 }
 
 pjsip_transport *
-SipTransport::createUdpTransport(const std::string &interface, unsigned int port, std::string& publicAddr, unsigned int publicPort)
+SipTransport::createUdpTransport(const std::string &interface, unsigned int port, const std::string &publicAddr, unsigned int publicPort)
 {
     // init socket to bind this transport to
     pj_uint16_t listeningPort = (pj_uint16_t) port;
     pjsip_transport *transport = NULL;
 
-    DEBUG("SipTransport: Update UDP transport on %s:%d with public addr %s:%d", interface.c_str(), port, publicAddr.c_str(), publicPort);
+    DEBUG("SipTransport: Update UDP transport on %s:%d with public addr %s:%d",
+            interface.c_str(), port, publicAddr.c_str(), publicPort);
 
     // determine the ip address for this transport
     std::string listeningAddress;
diff --git a/daemon/src/sip/siptransport.h b/daemon/src/sip/siptransport.h
index 3d5537e7dff49c520bbf79db11d42a44ed71ef7e..e37db61ae79a5178dd6147ed7074d3539fdc6ed2 100644
--- a/daemon/src/sip/siptransport.h
+++ b/daemon/src/sip/siptransport.h
@@ -140,7 +140,7 @@ class SipTransport {
          * @param The public address for this transport
          * @param The public port for this transport
          */
-        pjsip_transport *createUdpTransport(const std::string &interface, unsigned int port, std::string& publicAddr, unsigned int publicPort);
+        pjsip_transport *createUdpTransport(const std::string &interface, unsigned int port, const std::string &publicAddr, unsigned int publicPort);
 
     private:
         NON_COPYABLE(SipTransport);