diff --git a/arena.h b/arena.h
index 7ec4c8f..93baf15 100644
--- a/arena.h
+++ b/arena.h
@@ -33,7 +33,7 @@
 #ifndef ARENA_ASSERT
 #include <assert.h>
 #define ARENA_ASSERT assert
-#endif
+#endif // ARENA_ASSERT
 
 #define ARENA_BACKEND_LIBC_MALLOC 0
 #define ARENA_BACKEND_LINUX_MMAP 1