diff --git a/contrib/ports/unix/port/include/arch/cc.h b/contrib/ports/unix/port/include/arch/cc.h
index 6408abaa..3c44a099 100644
--- a/contrib/ports/unix/port/include/arch/cc.h
+++ b/contrib/ports/unix/port/include/arch/cc.h
@@ -56,7 +56,8 @@
 #define LWIP_ERRNO_STDINCLUDE	1
 #endif
 
-#define LWIP_RAND() ((u32_t)rand())
+extern unsigned int lwip_port_rand(void);
+#define LWIP_RAND() (lwip_port_rand())
 
 /* different handling for unit test, normally not needed */
 #ifdef LWIP_NOASSERT_ON_ERROR
diff --git a/contrib/ports/unix/port/sys_arch.c b/contrib/ports/unix/port/sys_arch.c
index bfebf324..070c6cff 100644
--- a/contrib/ports/unix/port/sys_arch.c
+++ b/contrib/ports/unix/port/sys_arch.c
@@ -68,6 +68,12 @@
 #include "lwip/stats.h"
 #include "lwip/tcpip.h"
 
+u32_t
+lwip_port_rand(void)
+{
+  return rand();
+}
+
 static void
 get_monotonic_time(struct timespec *ts)
 {