diff --git a/include/jemalloc/internal/jemalloc_internal_externs.h b/include/jemalloc/internal/jemalloc_internal_externs.h
index e10fb275..5beebc01 100644
--- a/include/jemalloc/internal/jemalloc_internal_externs.h
+++ b/include/jemalloc/internal/jemalloc_internal_externs.h
@@ -25,6 +25,9 @@ extern unsigned ncpus;
 /* Number of arenas used for automatic multiplexing of threads and arenas. */
 extern unsigned narenas_auto;
 
+/* Base index for manual arenas. */
+extern unsigned manual_arena_base;
+
 /*
  * Arenas that are used to service external requests.  Not all elements of the
  * arenas array are necessarily used; arenas are created lazily as needed.
diff --git a/include/jemalloc/internal/jemalloc_internal_inlines_b.h b/include/jemalloc/internal/jemalloc_internal_inlines_b.h
index 8b0ac462..70d6e578 100644
--- a/include/jemalloc/internal/jemalloc_internal_inlines_b.h
+++ b/include/jemalloc/internal/jemalloc_internal_inlines_b.h
@@ -71,9 +71,8 @@ arena_ichoose(tsd_t *tsd, arena_t *arena) {
 static inline bool
 arena_is_auto(arena_t *arena) {
 	assert(narenas_auto > 0);
-	unsigned offset = (opt_huge_threshold != 0) ? 1 : 0;
 
-	return (arena_ind_get(arena) < narenas_auto + offset);
+	return (arena_ind_get(arena) < manual_arena_base);
 }
 
 JEMALLOC_ALWAYS_INLINE extent_t *
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 594669c3..aded1398 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -86,8 +86,10 @@ malloc_mutex_t arenas_lock;
 JEMALLOC_ALIGNED(CACHELINE)
 atomic_p_t		arenas[MALLOCX_ARENA_LIMIT];
 static atomic_u_t	narenas_total; /* Use narenas_total_*(). */
-static arena_t		*a0; /* arenas[0]; read-only after initialization. */
-unsigned		narenas_auto; /* Read-only after initialization. */
+/* Below three are read-only after initialization. */
+static arena_t		*a0; /* arenas[0]. */
+unsigned		narenas_auto;
+unsigned		manual_arena_base;
 
 typedef enum {
 	malloc_init_uninitialized	= 3,
@@ -1322,6 +1324,7 @@ malloc_init_hard_a0_locked() {
 	 * malloc_ncpus().
 	 */
 	narenas_auto = 1;
+	manual_arena_base = narenas_auto + 1;
 	memset(arenas, 0, sizeof(arena_t *) * narenas_auto);
 	/*
 	 * Initialize one arena here.  The rest are lazily created in
@@ -1472,6 +1475,7 @@ malloc_init_narenas(void) {
 	if (arena_init_huge()) {
 		narenas_total_inc();
 	}
+	manual_arena_base = narenas_total_get();
 
 	return false;
 }