diff --git a/src/upnp.cpp b/src/upnp.cpp
index 2dc7ff1..215c9f4 100644
--- a/src/upnp.cpp
+++ b/src/upnp.cpp
@@ -24,6 +24,7 @@
 #include <sstream>
 #include <ciso646>
 #include <strings.h>
+#include <cassert>
 
 #if !defined(NDEBUG)
 #	define KUU_VERBOSE
@@ -51,11 +52,13 @@ namespace kuu {
 
 		struct UPNPUrlsWithInitFlag {
 			UPNPUrlsWithInitFlag() : initialized(false) {}
+			explicit UPNPUrlsWithInitFlag(std::nullptr_t) : initialized(false) {}
+			explicit UPNPUrlsWithInitFlag(bool parInit) : initialized(parInit) {}
 			struct UPNPUrls urls;
 			bool initialized;
 
-			operator struct UPNPUrls* () { return &urls; }
-			UPNPUrlsWithInitFlag* operator-> () { return this; }
+			operator struct UPNPUrls* () { return (initialized ? &urls : nullptr); }
+			UPNPUrls* operator-> () { return (initialized ? &urls : nullptr); }
 			bool operator not() const { return not initialized; }
 		};
 
@@ -179,15 +182,19 @@ namespace kuu {
 			throw ScanException("More than one UPNP device found (" + std::to_string(devs.size()) + ")");
 
 		UPNPUrlsPtr urls;
+		assert(not urls.get());
 		{
+			UPNPUrlsWithInitFlag urls_local(true);
+			assert(urls_local.initialized);
 			std::array<char, 64> lanaddr;
 			const auto i = UPNP_GetValidIGD(
 				devlist.get(),
-				urls.get(),
+				urls_local,
 				&m_local_data->data,
 				lanaddr.data(),
 				lanaddr.size()
 			);
+			urls.reset(urls_local);
 
 			switch (i) {
 			case 1:
@@ -198,14 +205,13 @@ namespace kuu {
 			default:
 				m_local_data->igd_reply = IGDNotSure;
 			}
-			urls->initialized = true;
 
 			m_local_data->lanaddr = lanaddr.data();
 		}
 
 		{
 			std::array<char, 64> externaladdr;
-			const auto r = UPNP_GetExternalIPAddress(urls->urls.controlURL, m_local_data->data.first.servicetype, externaladdr.data());
+			const auto r = UPNP_GetExternalIPAddress(urls->controlURL, m_local_data->data.first.servicetype, externaladdr.data());
 			if (UPNPCOMMAND_SUCCESS != r)
 				m_local_data->externaladdr = externaladdr.data();
 		}
@@ -254,7 +260,7 @@ namespace kuu {
 			intClient[0] = '\0';
 
 			r = UPNP_GetGenericPortMappingEntry(
-				m_local_data->urls->urls.controlURL,
+				m_local_data->urls->controlURL,
 				m_local_data->data.first.servicetype,
 				std::to_string(z).c_str(),
 				extPort,
@@ -299,7 +305,7 @@ namespace kuu {
 		Protocol parProtocol
 	) {
 		const auto r = UPNP_AddPortMapping(
-			m_local_data->urls->urls.controlURL,
+			m_local_data->urls->controlURL,
 			m_local_data->data.first.servicetype,
 			std::to_string(parExtPort).c_str(),
 			std::to_string(parIntPort).c_str(),
@@ -312,7 +318,7 @@ namespace kuu {
 		if (UPNPCOMMAND_SUCCESS != r) {
 			std::ostringstream oss;
 			oss << "Error in UPNP_AddPortMapping(\"" <<
-				m_local_data->urls->urls.controlURL << "\", \"" <<
+				m_local_data->urls->controlURL << "\", \"" <<
 				m_local_data->data.first.servicetype << "\", " <<
 				parExtPort << ", " <<
 				parIntPort << ", \"" <<