diff --git a/src/proxy.c b/src/proxy.c
index 3529085ee..06c3fb877 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -47,6 +47,7 @@
 #include <haproxy/lb_ss.h>
 #include <haproxy/log.h>
 #include <haproxy/obj_type-t.h>
+#include <haproxy/openssl-compat.h> /* required for TLSEXT_TYPE_application_layer_protocol_negotiation */
 #include <haproxy/peers.h>
 #include <haproxy/pool.h>
 #include <haproxy/protocol.h>