diff --git a/compiler-rt/lib/hwasan/hwasan_thread.h b/compiler-rt/lib/hwasan/hwasan_thread.h
--- a/compiler-rt/lib/hwasan/hwasan_thread.h
+++ b/compiler-rt/lib/hwasan/hwasan_thread.h
@@ -61,7 +61,7 @@
   void DisableTagging() { tagging_disabled_++; }
   void EnableTagging() { tagging_disabled_--; }
 
-  u64 unique_id() const { return unique_id_; }
+  u32 unique_id() const { return unique_id_; }
   void Announce() {
     if (announced_) return;
     announced_ = true;
@@ -89,7 +89,7 @@
   HeapAllocationsRingBuffer *heap_allocations_;
   StackAllocationsRingBuffer *stack_allocations_;
 
-  u64 unique_id_;  // counting from zero.
+  u32 unique_id_;  // counting from zero.
 
   u32 tagging_disabled_;  // if non-zero, malloc uses zero tag in this thread.