diff --git a/malloc.c b/malloc.c
index b6d9866..603d476 100644
--- a/malloc.c
+++ b/malloc.c
@@ -257,7 +257,7 @@ static size_t get_free_slot(struct random_state *rng, size_t slots, struct slab_
     }
 
     // randomize start location for linear search (uniform random choice is too slow)
-    uint64_t random_split = ~0UL >> get_random_size_uniform(rng, slots);
+    uint64_t random_split = ~(~0UL << get_random_size_uniform(rng, slots));
 
     size_t slot = ffzl(masked | random_split);
     if (slot) {