diff --git a/src/lib/upnp/Discovery.cxx b/src/lib/upnp/Discovery.cxx
index 9ea78c624..1539e1512 100644
--- a/src/lib/upnp/Discovery.cxx
+++ b/src/lib/upnp/Discovery.cxx
@@ -26,6 +26,7 @@
 
 #include <upnp/upnptools.h>
 
+#include <stdlib.h>
 #include <string.h>
 
 // The service type string we are looking for.