diff --git a/src/arena.c b/src/arena.c
index 9e91082..2476b01 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -12,15 +12,15 @@ static MemoryBlock *memoryblock_allocate(U32 size, U32 commit_size, U32 page_siz
     Assert(block != NULL);
     memory_commit(block, commit_size);
 
+    ASAN_POISON_MEMORY_REGION(block, size);
+    ASAN_UNPOISON_MEMORY_REGION(block, MemoryBlock_Header_Size);
+
     block->base          = (U8 *)block;
     block->size          = size;
     block->first_free    = MemoryBlock_Header_Size;
     block->arena_offset  = 0;
     block->prev          = NULL;
     block->committed_end = commit_size;
-
-    ASAN_POISON_MEMORY_REGION(block->base, block->size);
-    ASAN_UNPOISON_MEMORY_REGION(block, MemoryBlock_Header_Size);
     return block;
 }