diff --git a/include/haproxy/extcheck.h b/include/haproxy/extcheck.h
index 762971951..6186bee9a 100644
--- a/include/haproxy/extcheck.h
+++ b/include/haproxy/extcheck.h
@@ -35,7 +35,7 @@ int proxy_parse_extcheck(char **args, int section, struct proxy *curpx,
                          struct proxy *defpx, const char *file, int line,
                          char **errmsg);
 
-int proxy_parse_external_check_opt(char **args, int cur_arg, struct proxy *curpx, struct proxy *defpx,
+int proxy_parse_external_check_opt(char **args, int cur_arg, struct proxy *curpx, const struct proxy *defpx,
                                    const char *file, int line);
 
 
diff --git a/src/extcheck.c b/src/extcheck.c
index 6665e96bf..9ef87c55b 100644
--- a/src/extcheck.c
+++ b/src/extcheck.c
@@ -648,7 +648,7 @@ int proxy_parse_extcheck(char **args, int section, struct proxy *curpx,
 	return -1;
 }
 
-int proxy_parse_external_check_opt(char **args, int cur_arg, struct proxy *curpx, struct proxy *defpx,
+int proxy_parse_external_check_opt(char **args, int cur_arg, struct proxy *curpx, const struct proxy *defpx,
 				   const char *file, int line)
 {
 	int err_code = 0;