diff --git a/include/proto/protocol.h b/include/proto/protocol.h
index 7bbebb8..f25f77f 100644
--- a/include/proto/protocol.h
+++ b/include/proto/protocol.h
@@ -23,9 +23,11 @@
 #define _PROTO_PROTOCOL_H
 
 #include <sys/socket.h>
+#include <common/hathreads.h>
 #include <types/protocol.h>
 
 extern struct protocol *__protocol_by_family[AF_CUST_MAX];
+__decl_hathreads(extern HA_SPINLOCK_T proto_lock);
 
 /* Registers the protocol <proto> */
 void protocol_register(struct protocol *proto);
diff --git a/include/types/protocol.h b/include/types/protocol.h
index 1d3404b..f38baeb 100644
--- a/include/types/protocol.h
+++ b/include/types/protocol.h
@@ -80,9 +80,9 @@
 	int (*pause)(struct listener *l);               /* temporarily pause this listener for a soft restart */
 	void (*add)(struct listener *l, int port);      /* add a listener for this protocol and port */
 
-	struct list listeners;				/* list of listeners using this protocol */
-	int nb_listeners;				/* number of listeners */
-	struct list list;				/* list of registered protocols */
+	struct list listeners;				/* list of listeners using this protocol (under proto_lock) */
+	int nb_listeners;				/* number of listeners (under proto_lock) */
+	struct list list;				/* list of registered protocols (under proto_lock) */
 };
 
 #define CONNECT_HAS_DATA                        0x00000001 /* There's data available to be sent */