diff --git a/include/proto/connection.h b/include/proto/connection.h
index 952f9ea2f..f50329c38 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -35,9 +35,9 @@ extern struct pool_head *pool2_connection;
 int init_connection();
 
 /* I/O callback for fd-based connections. It calls the read/write handlers
- * provided by the connection's sock_ops. Returns 0.
+ * provided by the connection's sock_ops.
  */
-int conn_fd_handler(int fd);
+void conn_fd_handler(int fd);
 
 /* receive a PROXY protocol header over a connection */
 int conn_recv_proxy(struct connection *conn, int flag);
diff --git a/include/proto/listener.h b/include/proto/listener.h
index 1473bfda7..75bae86d9 100644
--- a/include/proto/listener.h
+++ b/include/proto/listener.h
@@ -105,7 +105,7 @@ void delete_listener(struct listener *listener);
  * to an accept. It tries to accept as many connections as possible, and for each
  * calls the listener's accept handler (generally the frontend's accept handler).
  */
-int listener_accept(int fd);
+void listener_accept(int fd);
 
 /*
  * Registers the bind keyword list <kwl> as a list of valid keywords for next
diff --git a/include/proto/proto_udp.h b/include/proto/proto_udp.h
index c452a10b9..d1f0698c6 100644
--- a/include/proto/proto_udp.h
+++ b/include/proto/proto_udp.h
@@ -22,6 +22,6 @@
 #ifndef _PROTO_PROTO_UDP_H
 #define _PROTO_PROTO_UDP_H
 
-int dgram_fd_handler(int);
+void dgram_fd_handler(int);
 
 #endif // _PROTO_PROTO_UDP_H
diff --git a/include/types/fd.h b/include/types/fd.h
index 057d968ad..8299a0264 100644
--- a/include/types/fd.h
+++ b/include/types/fd.h
@@ -78,7 +78,7 @@ enum fd_states {
 
 /* info about one given fd */
 struct fdtab {
-	int (*iocb)(int fd);                 /* I/O handler, returns FD_WAIT_* */
+	void (*iocb)(int fd);                /* I/O handler */
 	void *owner;                         /* the connection or listener associated with this fd, NULL if closed */
 	unsigned int  cache;                 /* position+1 in the FD cache. 0=not in cache. */
 	unsigned char state;                 /* FD state for read and write directions (2*3 bits) */
diff --git a/include/types/protocol.h b/include/types/protocol.h
index 74b20e8fa..6a4986ff4 100644
--- a/include/types/protocol.h
+++ b/include/types/protocol.h
@@ -50,7 +50,7 @@ struct protocol {
 	sa_family_t sock_family;			/* socket family, for sockaddr */
 	socklen_t sock_addrlen;				/* socket address length, used by bind() */
 	int l3_addrlen;					/* layer3 address length, used by hashes */
-	int (*accept)(int fd);				/* generic accept function */
+	void (*accept)(int fd);				/* generic accept function */
 	int (*bind)(struct listener *l, char *errmsg, int errlen); /* bind a listener */
 	int (*bind_all)(struct protocol *proto, char *errmsg, int errlen); /* bind all unbound listeners */
 	int (*unbind_all)(struct protocol *proto);	/* unbind all bound listeners */
diff --git a/src/connection.c b/src/connection.c
index b8be0a106..330f3efbc 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -36,15 +36,15 @@ int init_connection()
 }
 
 /* I/O callback for fd-based connections. It calls the read/write handlers
- * provided by the connection's sock_ops, which must be valid. It returns 0.
+ * provided by the connection's sock_ops, which must be valid.
  */
-int conn_fd_handler(int fd)
+void conn_fd_handler(int fd)
 {
 	struct connection *conn = fdtab[fd].owner;
 	unsigned int flags;
 
 	if (unlikely(!conn))
-		return 0;
+		return;
 
 	conn_refresh_polling_flags(conn);
 	flags = conn->flags & ~CO_FL_ERROR; /* ensure to call the wake handler upon error */
@@ -86,7 +86,7 @@ int conn_fd_handler(int fd)
 	 * we must not use it anymore and should immediately leave instead.
 	 */
 	if ((conn->flags & CO_FL_INIT_DATA) && conn->data->init(conn) < 0)
-		return 0;
+		return;
 
 	/* The data transfer starts here and stops on error and handshakes. Note
 	 * that we must absolutely test conn->xprt at each step in case it suddenly
@@ -133,7 +133,7 @@ int conn_fd_handler(int fd)
 	if ((conn->flags & CO_FL_WAKE_DATA) &&
 	    ((conn->flags ^ flags) & CO_FL_CONN_STATE) &&
 	    conn->data->wake(conn) < 0)
-		return 0;
+		return;
 
 	/* Last check, verify if the connection just established */
 	if (unlikely(!(conn->flags & (CO_FL_WAIT_L4_CONN | CO_FL_WAIT_L6_CONN | CO_FL_CONNECTED))))
@@ -144,7 +144,7 @@ int conn_fd_handler(int fd)
 
 	/* commit polling changes */
 	conn_cond_update_polling(conn);
-	return 0;
+	return;
 }
 
 /* Update polling on connection <c>'s file descriptor depending on its current
diff --git a/src/listener.c b/src/listener.c
index 5abeb806f..566b34082 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -32,6 +32,7 @@
 #include <proto/fd.h>
 #include <proto/freq_ctr.h>
 #include <proto/log.h>
+#include <proto/listener.h>
 #include <proto/sample.h>
 #include <proto/stream.h>
 #include <proto/task.h>
diff --git a/src/proto_udp.c b/src/proto_udp.c
index 0e361d928..c4434d78e 100644
--- a/src/proto_udp.c
+++ b/src/proto_udp.c
@@ -17,17 +17,17 @@
 #include <proto/fd.h>
 
 /* datagram handler callback */
-int dgram_fd_handler(int fd)
+void dgram_fd_handler(int fd)
 {
 	struct dgram_conn *dgram = fdtab[fd].owner;
 
 	if (unlikely(!dgram))
-		return 0;
+		return;
 
 	if (fd_recv_ready(fd))
 		dgram->data->recv(dgram);
 	else if (fd_send_ready(fd))
 		dgram->data->send(dgram);
 
-	return 0;
+	return;
 }