diff --git a/mem/src/arena/mem_arena.c b/mem/src/arena/mem_arena.c
index ae3ba04..330259f 100644
--- a/mem/src/arena/mem_arena.c
+++ b/mem/src/arena/mem_arena.c
@@ -6,6 +6,8 @@
 #include <string.h>
 
 #ifndef DEFAULT_ALIGNMENT
+// Why 2 * sizeof(void *) instead of sizeof(void *)
+// https://handmade.network/forums/t/6860-alignment_arena_allocator
 #define DEFAULT_ALIGNMENT (2 * sizeof(void *))
 #endif /* ifndef DEFAULT_ALIGNMENT */