diff --git a/src/bip.c b/src/bip.c
index ac0ce6f..ca8159b 100644
--- a/src/bip.c
+++ b/src/bip.c
@@ -131,7 +131,7 @@ static int add_server(bip_t *bip, struct server *s, list_t *data)
 #define ERRBUFSZ 128
 
 extern list_t *root_list;
-extern int yyparse();
+extern int yyparse(void);
 
 void conf_die(bip_t *bip, char *fmt, ...)
 {
@@ -1101,7 +1101,7 @@ out_conf_error:
 	return 0;
 }
 
-void check_rlimits()
+void check_rlimits(void)
 {
 	int r, cklim;
 	struct rlimit lt;
diff --git a/src/bip_main.c b/src/bip_main.c
index 22570a5..858a237 100644
--- a/src/bip_main.c
+++ b/src/bip_main.c
@@ -2,7 +2,8 @@
  * $Id: bip.c,v 1.39 2005/04/21 06:58:50 nohar Exp $
  *
  * This file is part of the bip project
- * Copyright (C) 2004 2005 Arnaud Cornet and Loïc Gomez
+ * Copyright (C) 2004,2005 Arnaud Cornet
+ * Copyright (C) 2004,2005,2022 Loïc Gomez
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -62,7 +63,7 @@ extern FILE *conf_global_log_file;
 
 void reload_config(int i);
 void bad_quit(int i);
-void check_rlimits();
+void check_rlimits(void);
 void rlimit_cpu_reached(int i);
 void rlimit_bigfile_reached(int i);
 void conf_die(bip_t *bip, char *fmt, ...);
@@ -83,7 +84,7 @@ static void usage(char *name)
 	exit(1);
 }
 
-static void version()
+static void version(void)
 {
 	printf(
 "Bip IRC Proxy - " PACKAGE_VERSION "\n"
diff --git a/src/conf.y b/src/conf.y
index ca735ee..d12cdda 100644
--- a/src/conf.y
+++ b/src/conf.y
@@ -4,6 +4,7 @@
  *
  * This file is part of the bip proproject
  * Copyright (C) 2004 Arnaud Cornet
+ * Copyright (C) 2022 Loïc Gomez
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -24,7 +25,7 @@ extern int linec;
 
 extern int yyerror(char *);
 
-int yywrap()
+int yywrap(void)
 {
 	return 1;
 }
diff --git a/src/irc.c b/src/irc.c
index 8ad6ba1..056b298 100644
--- a/src/irc.c
+++ b/src/irc.c
@@ -2753,7 +2753,7 @@ void irc_client_free(struct link_client *cli)
 	free(cli);
 }
 
-struct link *irc_link_new()
+struct link *irc_link_new(void)
 {
 	struct link *link;
 	link = bip_calloc(sizeof(struct link), 1);
diff --git a/src/irc.h b/src/irc.h
index 1e26d72..5d7a4c8 100644
--- a/src/irc.h
+++ b/src/irc.h
@@ -272,12 +272,12 @@ void bip_init(bip_t *bip);
 struct link_client *irc_client_new(void);
 struct link_server *irc_server_new(struct link *link, connection_t *conn);
 void irc_server_free(struct link_server *is);
-struct client *client_new();
+struct client *client_new(void);
 void irc_main(bip_t *);
 int ischannel(char p);
 void irc_client_close(struct link_client *);
 void irc_client_free(struct link_client *);
-struct link *irc_link_new();
+struct link *irc_link_new(void);
 void link_kill(bip_t *bip, struct link *);
 void unbind_from_link(struct link_client *ic);
 char *nick_from_ircmask(const char *mask);