diff --git a/include/jemalloc/internal/arena_structs_b.h b/include/jemalloc/internal/arena_structs_b.h
index 369b4cd2..612b4e7d 100644
--- a/include/jemalloc/internal/arena_structs_b.h
+++ b/include/jemalloc/internal/arena_structs_b.h
@@ -39,6 +39,11 @@ struct arena_bin_info_s {
 struct arena_decay_s {
 	/* Synchronizes all non-atomic fields. */
 	malloc_mutex_t		mtx;
+	/*
+	 * True if a thread is currently purging the extents associated with
+	 * this decay structure.
+	 */
+	bool			purging;
 	/*
 	 * Approximate time in seconds from the creation of a set of unused
 	 * dirty pages until an equivalent set of unused dirty pages is purged
@@ -199,13 +204,6 @@ struct arena_s {
 	 */
 	arena_decay_t		decay;
 
-	/*
-	 * True if a thread is currently executing arena_purge_to_limit().
-	 *
-	 * Synchronization: decay.mtx.
-	 */
-	bool			purging;
-
 	/*
 	 * Next extent size class in a growing series to use when satisfying a
 	 * request via the extent hooks (only if !config_munmap).  This limits
diff --git a/src/arena.c b/src/arena.c
index ea8e6a55..c253760b 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -663,6 +663,7 @@ arena_decay_init(arena_decay_t *decay, extents_t *extents, ssize_t decay_time) {
 	if (malloc_mutex_init(&decay->mtx, "decay", WITNESS_RANK_DECAY)) {
 		return true;
 	}
+	decay->purging = false;
 	arena_decay_reinit(decay, extents, decay_time);
 	return false;
 }
@@ -812,10 +813,10 @@ arena_purge_to_limit(tsdn_t *tsdn, arena_t *arena, arena_decay_t *decay,
 	witness_assert_depth_to_rank(tsdn, WITNESS_RANK_CORE, 1);
 	malloc_mutex_assert_owner(tsdn, &decay->mtx);
 
-	if (arena->purging) {
+	if (decay->purging) {
 		return;
 	}
-	arena->purging = true;
+	decay->purging = true;
 
 	extent_hooks_t *extent_hooks = extent_hooks_get(arena);
 	size_t npurge, npurged;
@@ -845,7 +846,7 @@ arena_purge_to_limit(tsdn_t *tsdn, arena_t *arena, arena_decay_t *decay,
 	}
 
 label_return:
-	arena->purging = false;
+	decay->purging = false;
 }
 
 void
@@ -1747,8 +1748,6 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
 		goto label_error;
 	}
 
-	arena->purging = false;
-
 	if (!config_munmap) {
 		arena->extent_grow_next = psz2ind(HUGEPAGE);
 	}