diff --git a/agent/qrexec-fork-server.c b/agent/qrexec-fork-server.c
index e9bcab7..655d138 100644
--- a/agent/qrexec-fork-server.c
+++ b/agent/qrexec-fork-server.c
@@ -32,6 +32,7 @@
 #include <libvchan.h>
 #include "libqrexec-utils.h"
 #include "qrexec-agent.h"
+#undef _FORTIFY_SOURCE
 
 extern char **environ;
 const bool qrexec_is_fork_server = true;