diff --git a/test/unit/lwipopts.h b/test/unit/lwipopts.h
index 2e94d4f9..94a1ecb9 100644
--- a/test/unit/lwipopts.h
+++ b/test/unit/lwipopts.h
@@ -67,7 +67,7 @@
 /* Minimal changes to opt.h required for etharp unit tests: */
 #define ETHARP_SUPPORT_STATIC_ENTRIES   1
 
-#define MEMP_NUM_SYS_TIMEOUT            (LWIP_NUM_SYS_TIMEOUT_INTERNAL + 5)
+#define MEMP_NUM_SYS_TIMEOUT            (LWIP_NUM_SYS_TIMEOUT_INTERNAL + 8)
 
 /* MIB2 stats are required to check IPv4 reassembly results */
 #define MIB2_STATS                      1