diff -uNr moc-2.5.2/main.c moc-2.5.2.mod/main.c
--- moc-2.5.2/main.c	2016-11-16 02:54:37.000000000 +0200
+++ moc-2.5.2.mod/main.c	2020-01-02 16:01:04.339045422 +0200
@@ -46,6 +46,11 @@
 #include "files.h"
 #include "rcc.h"
 
+#ifndef SUN_LEN
+# define SUN_LEN(ptr) ((size_t) (((struct sockaddr_un *) 0)->sun_path)        \
+                      + strlen ((ptr)->sun_path))
+#endif
+
 struct parameters
 {
 	char *config_file;
diff -uNr moc-2.5.2/server.c moc-2.5.2.mod/server.c
--- moc-2.5.2/server.c	2016-11-16 02:54:37.000000000 +0200
+++ moc-2.5.2.mod/server.c	2020-01-02 16:00:50.770930819 +0200
@@ -52,6 +52,11 @@
 #define SERVER_LOG	"mocp_server_log"
 #define PID_FILE	"pid"
 
+#ifndef SUN_LEN
+# define SUN_LEN(ptr) ((size_t) (((struct sockaddr_un *) 0)->sun_path)        \
+                      + strlen ((ptr)->sun_path))
+#endif
+
 struct client
 {
 	int socket; 		/* -1 if inactive */