diff --git a/local_cache.h b/local_cache.h
index 43cbc68..5003937 100644
--- a/local_cache.h
+++ b/local_cache.h
@@ -135,6 +135,7 @@
   struct PerClass {
     u32 Count;
     u32 MaxCount;
+    // Note: ClassSize is zero for the transfer batch.
     uptr ClassSize;
     CompactPtrT Chunks[2 * TransferBatch::MaxNumCached];
   };
@@ -154,7 +155,13 @@
       PerClass *P = &PerClassArray[I];
       const uptr Size = SizeClassAllocator::getSizeByClassId(I);
       P->MaxCount = 2 * TransferBatch::getMaxCached(Size);
-      P->ClassSize = Size;
+      if (I != BatchClassId) {
+        P->ClassSize = Size;
+      } else {
+        // ClassSize in this struct is only used for malloc/free stats, which
+        // should only track user allocations, not internal movements.
+        P->ClassSize = 0;
+      }
     }
   }