diff --git a/include/jemalloc/internal/arena_externs.h b/include/jemalloc/internal/arena_externs.h
index 4ef8d8e8..8548b1f0 100644
--- a/include/jemalloc/internal/arena_externs.h
+++ b/include/jemalloc/internal/arena_externs.h
@@ -81,7 +81,6 @@ bool arena_retain_grow_limit_get_set(tsd_t *tsd, arena_t *arena,
 unsigned arena_nthreads_get(arena_t *arena, bool internal);
 void arena_nthreads_inc(arena_t *arena, bool internal);
 void arena_nthreads_dec(arena_t *arena, bool internal);
-size_t arena_extent_sn_next(arena_t *arena);
 arena_t *arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks);
 bool arena_init_huge(void);
 bool arena_is_huge(unsigned arena_ind);
diff --git a/include/jemalloc/internal/arena_structs.h b/include/jemalloc/internal/arena_structs.h
index 7d312343..ca11af71 100644
--- a/include/jemalloc/internal/arena_structs.h
+++ b/include/jemalloc/internal/arena_structs.h
@@ -121,13 +121,6 @@ struct arena_s {
 	/* Synchronization: internal. */
 	counter_accum_t		prof_accum;
 
-	/*
-	 * Extent serial number generator state.
-	 *
-	 * Synchronization: atomic.
-	 */
-	atomic_zu_t		extent_sn_next;
-
 	/*
 	 * Represents a dss_prec_t, but atomically.
 	 *
diff --git a/include/jemalloc/internal/pa.h b/include/jemalloc/internal/pa.h
index 1b9e58c4..29c6b211 100644
--- a/include/jemalloc/internal/pa.h
+++ b/include/jemalloc/internal/pa.h
@@ -46,11 +46,15 @@ struct pa_shard_s {
 	/* The grow info for the retained ecache. */
 	ecache_grow_t ecache_grow;
 
+	/* Extent serial number generator state. */
+	atomic_zu_t extent_sn_next;
+
 	pa_shard_stats_t *stats;
 };
 
 /* Returns true on error. */
 bool pa_shard_init(tsdn_t *tsdn, pa_shard_t *shard, base_t *base, unsigned ind,
     pa_shard_stats_t *stats);
+size_t pa_shard_extent_sn_next(pa_shard_t *shard);
 
 #endif /* JEMALLOC_INTERNAL_PA_H */
diff --git a/src/arena.c b/src/arena.c
index a29dc937..8f306604 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -1979,11 +1979,6 @@ arena_nthreads_dec(arena_t *arena, bool internal) {
 	atomic_fetch_sub_u(&arena->nthreads[internal], 1, ATOMIC_RELAXED);
 }
 
-size_t
-arena_extent_sn_next(arena_t *arena) {
-	return atomic_fetch_add_zu(&arena->extent_sn_next, 1, ATOMIC_RELAXED);
-}
-
 arena_t *
 arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
 	arena_t *arena;
@@ -2032,8 +2027,6 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
 		}
 	}
 
-	atomic_store_zu(&arena->extent_sn_next, 0, ATOMIC_RELAXED);
-
 	atomic_store_u(&arena->dss_prec, (unsigned)extent_dss_prec_get(),
 	    ATOMIC_RELAXED);
 
diff --git a/src/extent.c b/src/extent.c
index 51062642..918738d6 100644
--- a/src/extent.c
+++ b/src/extent.c
@@ -662,8 +662,9 @@ extent_grow_retained(tsdn_t *tsdn, arena_t *arena, ehooks_t *ehooks,
 	}
 
 	edata_init(edata, ecache_ind_get(&arena->pa_shard.ecache_retained), ptr,
-	    alloc_size, false, SC_NSIZES, arena_extent_sn_next(arena),
-	    extent_state_active, zeroed, committed, true, EXTENT_IS_HEAD);
+	    alloc_size, false, SC_NSIZES,
+	    pa_shard_extent_sn_next(&arena->pa_shard), extent_state_active,
+	    zeroed, committed, true, EXTENT_IS_HEAD);
 
 	if (extent_register_no_gdump_add(tsdn, edata)) {
 		edata_cache_put(tsdn, &arena->pa_shard.edata_cache, edata);
@@ -816,8 +817,8 @@ extent_alloc_wrapper(tsdn_t *tsdn, arena_t *arena, ehooks_t *ehooks,
 		return NULL;
 	}
 	edata_init(edata, ecache_ind_get(&arena->pa_shard.ecache_dirty), addr,
-	    size, slab, szind, arena_extent_sn_next(arena), extent_state_active,
-	    *zero, *commit, true, EXTENT_NOT_HEAD);
+	    size, slab, szind, pa_shard_extent_sn_next(&arena->pa_shard),
+	    extent_state_active, *zero, *commit, true, EXTENT_NOT_HEAD);
 	if (extent_register(tsdn, edata)) {
 		edata_cache_put(tsdn, &arena->pa_shard.edata_cache, edata);
 		return NULL;
diff --git a/src/extent_dss.c b/src/extent_dss.c
index d125c439..7746a208 100644
--- a/src/extent_dss.c
+++ b/src/extent_dss.c
@@ -155,9 +155,9 @@ 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, arena_extent_sn_next(arena),
-				    extent_state_active, false, true, true,
-				    EXTENT_NOT_HEAD);
+				    SC_NSIZES, pa_shard_extent_sn_next(
+					&arena->pa_shard), extent_state_active,
+				    false, true, true, EXTENT_NOT_HEAD);
 			}
 			/*
 			 * Compute the address just past the end of the desired
diff --git a/src/pa.c b/src/pa.c
index 5063d48f..35d3335f 100644
--- a/src/pa.c
+++ b/src/pa.c
@@ -42,8 +42,15 @@ pa_shard_init(tsdn_t *tsdn, pa_shard_t *shard, base_t *base, unsigned ind,
 		return true;
 	}
 
+	atomic_store_zu(&shard->extent_sn_next, 0, ATOMIC_RELAXED);
+
 	shard->stats = stats;
 	memset(shard->stats, 0, sizeof(*shard->stats));
 
 	return false;
 }
+
+size_t
+pa_shard_extent_sn_next(pa_shard_t *shard) {
+	return atomic_fetch_add_zu(&shard->extent_sn_next, 1, ATOMIC_RELAXED);
+}