diff --git a/include/haproxy/tcpcheck.h b/include/haproxy/tcpcheck.h
index a8a36a709..29b4c9b21 100644
--- a/include/haproxy/tcpcheck.h
+++ b/include/haproxy/tcpcheck.h
@@ -47,7 +47,7 @@ void deinit_proxy_tcpcheck(struct proxy *px);
 
 struct tcpcheck_var *create_tcpcheck_var(const struct ist name);
 void free_tcpcheck_var(struct tcpcheck_var *var);
-int dup_tcpcheck_vars(struct list *dst, struct list *src);
+int dup_tcpcheck_vars(struct list *dst, const struct list *src);
 void free_tcpcheck_vars(struct list *vars);
 
 int add_tcpcheck_expect_str(struct tcpcheck_rules *rules, const char *str);
diff --git a/src/tcpcheck.c b/src/tcpcheck.c
index 02c86afbc..94ba28f3e 100644
--- a/src/tcpcheck.c
+++ b/src/tcpcheck.c
@@ -254,9 +254,10 @@ void free_tcpcheck_vars(struct list *vars)
 }
 
 /* Duplicate a list of preset tcp-check variables */
-int dup_tcpcheck_vars(struct list *dst, struct list *src)
+int dup_tcpcheck_vars(struct list *dst, const struct list *src)
 {
-	struct tcpcheck_var *var, *new = NULL;
+	const struct tcpcheck_var *var;
+	struct tcpcheck_var *new = NULL;
 
 	list_for_each_entry(var, src, list) {
 		new = create_tcpcheck_var(var->name);