diff --git a/include/jemalloc/internal/extent.h b/include/jemalloc/internal/extent.h
index 2f14b81f..2eb53f66 100644
--- a/include/jemalloc/internal/extent.h
+++ b/include/jemalloc/internal/extent.h
@@ -48,7 +48,7 @@ edata_t *extent_split_wrapper(tsdn_t *tsdn, pa_shard_t *shard,
     ehooks_t *ehooks, edata_t *edata, size_t size_a, size_t size_b);
 bool extent_merge_wrapper(tsdn_t *tsdn, pa_shard_t *shard, ehooks_t *ehooks,
     edata_t *a, edata_t *b);
-
+size_t extent_sn_next(pac_t *pac);
 bool extent_boot(void);
 
 #endif /* JEMALLOC_INTERNAL_EXTENT_H */
diff --git a/include/jemalloc/internal/pa.h b/include/jemalloc/internal/pa.h
index 2891d7c4..e6ed1fd9 100644
--- a/include/jemalloc/internal/pa.h
+++ b/include/jemalloc/internal/pa.h
@@ -84,9 +84,6 @@ struct pa_shard_s {
 	/* The source of edata_t objects. */
 	edata_cache_t edata_cache;
 
-	/* Extent serial number generator state. */
-	atomic_zu_t extent_sn_next;
-
 	malloc_mutex_t *stats_mtx;
 	pa_shard_stats_t *stats;
 
@@ -131,8 +128,6 @@ void pa_shard_reset(pa_shard_t *shard);
  */
 void pa_shard_destroy_retained(tsdn_t *tsdn, pa_shard_t *shard);
 
-size_t pa_shard_extent_sn_next(pa_shard_t *shard);
-
 /* Gets an edata for the given allocation. */
 edata_t *pa_alloc(tsdn_t *tsdn, pa_shard_t *shard, size_t size,
     size_t alignment, bool slab, szind_t szind, bool zero);
diff --git a/include/jemalloc/internal/pac.h b/include/jemalloc/internal/pac.h
index 14ee09f3..d1d68534 100644
--- a/include/jemalloc/internal/pac.h
+++ b/include/jemalloc/internal/pac.h
@@ -90,6 +90,9 @@ struct pac_s {
 
 	malloc_mutex_t *stats_mtx;
 	pac_stats_t *stats;
+
+	/* Extent serial number generator state. */
+	atomic_zu_t extent_sn_next;
 };
 
 bool pac_init(tsdn_t *tsdn, pac_t *pac, unsigned ind, emap_t *emap,
diff --git a/src/extent.c b/src/extent.c
index fb6ccebd..bb5daba1 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -50,6 +50,11 @@ static edata_t *extent_alloc_retained(tsdn_t *tsdn, pa_shard_t *shard,
 
 /******************************************************************************/
 
+size_t
+extent_sn_next(pac_t *pac) {
+	return atomic_fetch_add_zu(&pac->extent_sn_next, 1, ATOMIC_RELAXED);
+}
+
 static bool
 extent_try_delayed_coalesce(tsdn_t *tsdn, pa_shard_t *shard,
     ehooks_t *ehooks, ecache_t *ecache, edata_t *edata) {
@@ -648,7 +653,7 @@ extent_grow_retained(tsdn_t *tsdn, pa_shard_t *shard, ehooks_t *ehooks,
 	}
 
 	edata_init(edata, ecache_ind_get(&shard->pac.ecache_retained), ptr,
-	    alloc_size, false, SC_NSIZES, pa_shard_extent_sn_next(shard),
+	    alloc_size, false, SC_NSIZES, extent_sn_next(&shard->pac),
 	    extent_state_active, zeroed, committed, /* ranged */ false,
 	    EXTENT_IS_HEAD);
 
@@ -793,7 +798,7 @@ extent_alloc_wrapper(tsdn_t *tsdn, pa_shard_t *shard, ehooks_t *ehooks,
 		return NULL;
 	}
 	edata_init(edata, ecache_ind_get(&shard->pac.ecache_dirty), addr,
-	    size, /* slab */ false, SC_NSIZES, pa_shard_extent_sn_next(shard),
+	    size, /* slab */ false, SC_NSIZES, extent_sn_next(&shard->pac),
 	    extent_state_active, zero, *commit, /* ranged */ false,
 	    EXTENT_NOT_HEAD);
 	if (extent_register(tsdn, shard, edata)) {
diff --git a/src/extent_dss.c b/src/extent_dss.c
index 81161b3a..dff231d9 100644
--- a/src/extent_dss.c
+++ b/src/extent_dss.c
@@ -154,9 +154,10 @@ extent_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
 			if (gap_size_page != 0) {
 				edata_init(gap, arena_ind_get(arena),
 				    gap_addr_page, gap_size_page, false,
-				    SC_NSIZES, pa_shard_extent_sn_next(
-					&arena->pa_shard), extent_state_active,
-				    false, true, false, EXTENT_NOT_HEAD);
+				    SC_NSIZES, extent_sn_next(
+					&arena->pa_shard.pac),
+				    extent_state_active, false, true, false,
+				    EXTENT_NOT_HEAD);
 			}
 			/*
 			 * Compute the address just past the end of the desired
diff --git a/src/pa.c b/src/pa.c
index 3ca8e35d..2f970c76 100644
--- a/src/pa.c
+++ b/src/pa.c
@@ -35,7 +35,6 @@ pa_shard_init(tsdn_t *tsdn, pa_shard_t *shard, emap_t *emap, base_t *base,
 		return true;
 	}
 
-	atomic_store_zu(&shard->extent_sn_next, 0, ATOMIC_RELAXED);
 	atomic_store_zu(&shard->nactive, 0, ATOMIC_RELAXED);
 
 	shard->stats_mtx = stats_mtx;
@@ -79,11 +78,6 @@ pa_shard_destroy_retained(tsdn_t *tsdn, pa_shard_t *shard) {
 	}
 }
 
-size_t
-pa_shard_extent_sn_next(pa_shard_t *shard) {
-	return atomic_fetch_add_zu(&shard->extent_sn_next, 1, ATOMIC_RELAXED);
-}
-
 static bool
 pa_shard_may_have_muzzy(pa_shard_t *shard) {
 	return pac_muzzy_decay_ms_get(&shard->pac) != 0;
diff --git a/src/pac.c b/src/pac.c
index 9192f54c..8ff6f1c8 100644
--- a/src/pac.c
+++ b/src/pac.c
@@ -49,6 +49,7 @@ pac_init(tsdn_t *tsdn, pac_t *pac, unsigned ind, emap_t *emap,
 	pac->edata_cache = edata_cache;
 	pac->stats = pac_stats;
 	pac->stats_mtx = stats_mtx;
+	atomic_store_zu(&pac->extent_sn_next, 0, ATOMIC_RELAXED);
 	return false;
 }