diff --git base/allocator/partition_allocator/src/partition_alloc/thread_cache.h base/allocator/partition_allocator/src/partition_alloc/thread_cache.h
index 381245c374382..c98aed1663517 100644
--- base/allocator/partition_allocator/src/partition_alloc/thread_cache.h
+++ base/allocator/partition_allocator/src/partition_alloc/thread_cache.h
@@ -184,7 +184,7 @@ class PA_COMPONENT_EXPORT(PARTITION_ALLOC) ThreadCacheRegistry {
   internal::base::TimeDelta periodic_purge_next_interval_;
   bool is_purging_configured_ = false;
 
-  uint8_t largest_active_bucket_index_ = internal::BucketIndexLookup::GetIndex(
+  uint16_t largest_active_bucket_index_ = internal::BucketIndexLookup::GetIndex(
       ThreadCacheLimits::kDefaultSizeThreshold);
 };