diff --git a/folly/memory/Arena.h b/folly/memory/Arena.h
index 31518068904..412b5f5277b 100644
--- a/folly/memory/Arena.h
+++ b/folly/memory/Arena.h
@@ -200,6 +200,7 @@ class Arena {
   void freeLargeBlocks() {
     largeBlocks_.clear_and_dispose([this](LargeBlock* b) {
       auto size = b->allocSize;
+      totalAllocatedSize_ -= size;
       b->~LargeBlock();
       AllocTraits::deallocate(alloc(), reinterpret_cast<char*>(b), size);
     });
diff --git a/folly/memory/test/ArenaTest.cpp b/folly/memory/test/ArenaTest.cpp
index 9b1e74196c5..ca2a5b27878 100644
--- a/folly/memory/test/ArenaTest.cpp
+++ b/folly/memory/test/ArenaTest.cpp
@@ -216,7 +216,7 @@ TEST(Arena, Clear) {
     }
 
     EXPECT_EQ(arena.bytesUsed(), bytesUsed);
-    EXPECT_GT(arena.totalSize(), totalSize);
+    EXPECT_EQ(arena.totalSize(), totalSize);
 
     arena.clear();
   }