diff --git a/src/include/lwip/arch.h b/src/include/lwip/arch.h
index 8469440d..690559a0 100644
--- a/src/include/lwip/arch.h
+++ b/src/include/lwip/arch.h
@@ -66,7 +66,7 @@
 #endif
 
 /** Define random number generator function of your system */
-#ifndef LWIP_RAND()
+#ifndef LWIP_RAND
 #define LWIP_RAND() ((u32_t)rand())
 #endif