diff --git a/include/jemalloc/internal/tsd.h b/include/jemalloc/internal/tsd.h
index 9408b2ca..5ac85e14 100644
--- a/include/jemalloc/internal/tsd.h
+++ b/include/jemalloc/internal/tsd.h
@@ -77,6 +77,7 @@ typedef ql_elm(tsd_t) tsd_link_t;
     O(iarena,			arena_t *,		arena_t *)	\
     O(arena,			arena_t *,		arena_t *)	\
     O(arenas_tdata,		arena_tdata_t *,	arena_tdata_t *)\
+    O(sec_shard,		uint8_t,		uint8_t)	\
     O(binshards,		tsd_binshards_t,	tsd_binshards_t)\
     O(tsd_link,			tsd_link_t,		tsd_link_t)	\
     O(in_hook,			bool,			bool)		\
@@ -106,6 +107,7 @@ typedef ql_elm(tsd_t) tsd_link_t;
     /* iarena */		NULL,					\
     /* arena */			NULL,					\
     /* arenas_tdata */		NULL,					\
+    /* sec_shard */		(uint8_t)-1,				\
     /* binshards */		TSD_BINSHARDS_ZERO_INITIALIZER,		\
     /* tsd_link */		{NULL},					\
     /* in_hook */		false,					\
diff --git a/src/sec.c b/src/sec.c
index f3c906bc..262d813d 100644
--- a/src/sec.c
+++ b/src/sec.c
@@ -61,14 +61,20 @@ sec_shard_pick(tsdn_t *tsdn, sec_t *sec) {
 		return &sec->shards[0];
 	}
 	tsd_t *tsd = tsdn_tsd(tsdn);
-	/*
-	 * Use the trick from Daniel Lemire's "A fast alternative to the modulo
-	 * reduction.  Use a 64 bit number to store 32 bits, since we'll
-	 * deliberately overflow when we multiply by the number of shards.
-	 */
-	uint64_t rand32 = prng_lg_range_u64(tsd_prng_statep_get(tsd), 32);
-	uint32_t idx = (uint32_t)((rand32 * (uint64_t)sec->nshards) >> 32);
-	return &sec->shards[idx];
+	uint8_t *idxp = tsd_sec_shardp_get(tsd);
+	if (*idxp == (uint8_t)-1) {
+		/*
+		 * First use; initialize using the trick from Daniel Lemire's
+		 * "A fast alternative to the modulo reduction.  Use a 64 bit
+		 * number to store 32 bits, since we'll deliberately overflow
+		 * when we multiply by the number of shards.
+		 */
+		uint64_t rand32 = prng_lg_range_u64(tsd_prng_statep_get(tsd), 32);
+		uint32_t idx = (uint32_t)((rand32 * (uint64_t)sec->nshards) >> 32);
+		assert(idx < (uint32_t)sec->nshards);
+		*idxp = (uint8_t)idx;
+	}
+	return &sec->shards[*idxp];
 }
 
 static edata_t *