diff --git a/addons/promex/service-prometheus.c b/addons/promex/service-prometheus.c
index ee7c38f..6a42a47 100644
--- a/addons/promex/service-prometheus.c
+++ b/addons/promex/service-prometheus.c
@@ -34,6 +34,7 @@
 #include <haproxy/stream.h>
 #include <haproxy/stream_interface.h>
 #include <haproxy/task.h>
+#include <haproxy/tools.h>
 #include <haproxy/version.h>
 
 /* Prometheus exporter applet states (appctx->st0) */