diff --git a/test/unit/lwipopts.h b/test/unit/lwipopts.h
index fb5038b9..9c105419 100644
--- a/test/unit/lwipopts.h
+++ b/test/unit/lwipopts.h
@@ -48,7 +48,7 @@
 #define TCP_WND                         (10 * TCP_MSS)
 #define LWIP_WND_SCALE                  1
 #define TCP_RCV_SCALE                   0
-#define PBUF_POOL_SIZE                  400 // pbuf tests need ~200KByte
+#define PBUF_POOL_SIZE                  400 /* pbuf tests need ~200KByte */
 
 /* Minimal changes to opt.h required for etharp unit tests: */
 #define ETHARP_SUPPORT_STATIC_ENTRIES   1