diff --git a/libs/http_server/microhttpd_server_p.cpp b/libs/http_server/microhttpd_server_p.cpp
index 17039f09..13d5c0ea 100644
--- a/libs/http_server/microhttpd_server_p.cpp
+++ b/libs/http_server/microhttpd_server_p.cpp
@@ -95,11 +95,14 @@ int MicrohttpdServerConnection::send_error() {
 }
 
 
-void log_callback(void * cls, const char * fm, va_list ap) {
+void log_callback(void * cls, const char * fmt, va_list ap) {
 	MicrohttpdServer * server = (MicrohttpdServer *)cls;
 	piCout << "log" << server;
 	if (!server) return;
-	piCout << server << fm << ap;
+	char buffer[1024];
+	memset(buffer, 0, 1024);
+	std::vsnprintf(buffer, 1024, fmt, ap);
+	piCout << buffer;
 }