diff --git a/include/haproxy/http_htx.h b/include/haproxy/http_htx.h
index 70df6806f..fbd4438de 100644
--- a/include/haproxy/http_htx.h
+++ b/include/haproxy/http_htx.h
@@ -70,7 +70,7 @@ struct buffer *http_load_errorfile(const char *file, char **errmsg);
 struct buffer *http_load_errormsg(const char *key, const struct ist msg, char **errmsg);
 struct buffer *http_parse_errorfile(int status, const char *file, char **errmsg);
 struct buffer *http_parse_errorloc(int errloc, int status, const char *url, char **errmsg);
-int proxy_dup_default_conf_errors(struct proxy *curpx, struct proxy *defpx, char **errmsg);
+int proxy_dup_default_conf_errors(struct proxy *curpx, const struct proxy *defpx, char **errmsg);
 void proxy_release_conf_errors(struct proxy *px);
 
 #endif /* _HAPROXY_HTTP_HTX_H */
diff --git a/src/http_htx.c b/src/http_htx.c
index bb3d8d0f0..e2e6ce1ef 100644
--- a/src/http_htx.c
+++ b/src/http_htx.c
@@ -2080,7 +2080,7 @@ static int post_check_errors()
 	return err_code;
 }
 
-int proxy_dup_default_conf_errors(struct proxy *curpx, struct proxy *defpx, char **errmsg)
+int proxy_dup_default_conf_errors(struct proxy *curpx, const struct proxy *defpx, char **errmsg)
 {
 	struct conf_errors *conf_err, *new_conf_err = NULL;
 	int ret = 0;