diff --git a/src/bitcoinrpc.cpp b/src/bitcoinrpc.cpp
index 6510377fdfc..a79d028244b 100644
--- a/src/bitcoinrpc.cpp
+++ b/src/bitcoinrpc.cpp
@@ -2450,7 +2450,7 @@ void ThreadRPCServer2(void* parg)
     }
     catch(boost::system::system_error &e)
     {
-        ThreadSafeMessageBox(strprintf(_("An error occurred while setting up the RPC port %i for listening: %s"), endpoint.port(), e.what()),
+        ThreadSafeMessageBox(strprintf(_("An error occurred while setting up the RPC port %u for listening: %s"), endpoint.port(), e.what()),
                              _("Error"), wxOK | wxMODAL);
         StartShutdown();
         return;