diff --git a/core/box/pool_free_v1_box.h b/core/box/pool_free_v1_box.h
index d1f513f6..139c4232 100644
--- a/core/box/pool_free_v1_box.h
+++ b/core/box/pool_free_v1_box.h
@@ -12,6 +12,7 @@
 #include "pool_config_box.h"      // For hak_pool_v1_free_fastsplit_enabled, etc
 #include "pool_stats_box.h"       // For g_pool_v1_flat_stats
 #include "pool_mid_desc_cache_box.h"  // For mid_desc_lookup_cached
+#include "pool_mid_inuse_deferred_box.h"  // For mid_inuse_dec_deferred
 
 #include <stdint.h>
 #include <stdatomic.h>
@@ -78,10 +79,10 @@ static inline void hak_pool_free_v1_fast_impl(void* raw, int class_idx, uintptr_
         }
     }
 
-    // Common tail: sample counter + inuse dec
+    // Common tail: sample counter + inuse dec (deferred)
     t_pool_rng ^= t_pool_rng << 13; t_pool_rng ^= t_pool_rng >> 17; t_pool_rng ^= t_pool_rng << 5;
     if ((t_pool_rng & ((1u<<g_count_sample_exp)-1u)) == 0u) g_pool.frees[class_idx]++;
-    mid_page_inuse_dec_and_maybe_dn(raw);
+    mid_inuse_dec_deferred(raw);
 }
 
 // ============================================================================
@@ -169,7 +170,7 @@ static inline void hak_pool_free_v1_slow_impl(void* ptr, size_t size, uintptr_t
 tail:
     t_pool_rng ^= t_pool_rng << 13; t_pool_rng ^= t_pool_rng >> 17; t_pool_rng ^= t_pool_rng << 5;
     if ((t_pool_rng & ((1u<<g_count_sample_exp)-1u)) == 0u) g_pool.frees[class_idx]++;
-    mid_page_inuse_dec_and_maybe_dn(raw);
+    mid_inuse_dec_deferred(raw);
 }
 
 // ============================================================================