diff --git a/src/mem.cpp b/src/mem.cpp
index da70f29..42f62e8 100644
--- a/src/mem.cpp
+++ b/src/mem.cpp
@@ -80,7 +80,6 @@ Arena *arena_alloc_sized(u64 init_res, u64 init_cmt)
     arena->cmt = cmt;
     arena->res = res;
     arena->align = 8;
-    arena->grow = true;
     arena->mem_used = arena->mem_peak_used = ARENA_HEADER_SIZE;
   }
 
@@ -102,14 +101,6 @@ void arena_release(Arena *arena)
   }
 }
 
-internal
-u64 arena_huge_push_threshold()
-{
-  u64 res = ARENA_RESERVE_SIZE;
-  u64 threshold = (res - ARENA_HEADER_SIZE) / 2 + 1;
-  return threshold;
-}
-
 internal
 void *arena_push_impl(Arena *arena, u64 size)
 {
@@ -117,44 +108,45 @@ void *arena_push_impl(Arena *arena, u64 size)
   u64 pos_mem = align_pow2(cur->pos, arena->align);
   u64 pos_new = pos_mem + size;
 
-  if (cur->res < pos_new && arena->grow) {
-    Arena *new_block;
-    if (size < arena_huge_push_threshold()) {
-      new_block = arena_alloc();
-    } else {
-      u64 new_block_size = size + ARENA_HEADER_SIZE;
-      new_block = arena_alloc_sized(new_block_size, new_block_size);
+  if (cur->res < pos_new) {
+    u64 res_size = cur->res;
+    u64 cmt_size = cur->cmt;
+    if (size > res_size) {
+      res_size = size + ARENA_HEADER_SIZE;
+      cmt_size = size + ARENA_HEADER_SIZE;
     }
+    Arena *new_block = arena_alloc_sized(res_size, cmt_size);
+    new_block->base_pos = cur->base_pos + cur->res;
+    new_block->prev = arena->cur;
+    arena->cur = new_block;
 
-    if (new_block) {
-      new_block->base_pos = cur->base_pos + cur->res;
-      new_block->prev = arena->cur;
-      arena->cur = new_block;
-
-      cur = new_block;
-      pos_mem = align_pow2(cur->pos, cur->align);
-      pos_new = pos_mem + size;
-    }
+    cur = new_block;
+    pos_mem = align_pow2(cur->pos, cur->align);
+    pos_new = pos_mem + size;
   }
 
   if (cur->cmt < pos_new) {
-    u64 cmt_new_aligned = align_pow2(pos_new, ARENA_COMMIT_SIZE);
+    u64 cmt_new_aligned = align_pow2(pos_new, cur->cmt);
     u64 cmt_new_clamped = min(cmt_new_aligned, cur->res);
     u64 cmt_new_size = cmt_new_clamped - cur->cmt;
-    b32x is_cmt_ok = os_commit((u8*)cur + cur->cmt, cmt_new_size);
-
-    if (is_cmt_ok)
-      cur->cmt = cmt_new_clamped;
+    os_commit((u8*)cur + cur->cmt, cmt_new_size);
+    cur->cmt = cmt_new_clamped;
   }
 
   void *mem = 0;
   if (cur->cmt >= pos_new) {
     mem = (u8*)cur + pos_mem;
     u64 added_size = pos_new - cur->pos;
+    assert(added_size >= size);
     arena->mem_used += added_size;
     arena->mem_peak_used = max(arena->mem_peak_used, arena->mem_used);
     cur->pos = pos_new;
-    asan_unpoison_memory_region(mem, added_size);
+    asan_unpoison_memory_region(mem, size);
+  }
+
+  if (UNLIKELY(!mem)) {
+    fprintf(stderr, "Failed to grow arena.\n");
+    exit(1);
   }
 
   return mem;
diff --git a/src/mem.h b/src/mem.h
index c2b8b6e..801b44a 100644
--- a/src/mem.h
+++ b/src/mem.h
@@ -12,7 +12,6 @@ struct Arena {
   u64 align;
   u64 mem_used;
   u64 mem_peak_used;
-  b8 grow;
 };
 
 struct Temp {