diff --git a/test/blockstore/interface/helpers/BlockStoreWithRandomKeysTest.cpp b/test/blockstore/interface/helpers/BlockStoreWithRandomKeysTest.cpp
index a3a1acef..689cf101 100644
--- a/test/blockstore/interface/helpers/BlockStoreWithRandomKeysTest.cpp
+++ b/test/blockstore/interface/helpers/BlockStoreWithRandomKeysTest.cpp
@@ -30,6 +30,7 @@ public:
   MOCK_METHOD1(do_load, Block*(const Key &));
   void remove(unique_ref<Block> block) {UNUSED(block);}
   MOCK_CONST_METHOD0(numBlocks, uint64_t());
+  MOCK_CONST_METHOD0(estimateNumFreeBytes, uint64_t());
 };
 
 class BlockMock: public Block {