diff --git a/libraries/chain/include/eosio/chain/incremental_merkle.hpp b/libraries/chain/include/eosio/chain/incremental_merkle.hpp
index 9325e3ed29..0b3d5dd4f4 100644
--- a/libraries/chain/include/eosio/chain/incremental_merkle.hpp
+++ b/libraries/chain/include/eosio/chain/incremental_merkle.hpp
@@ -19,7 +19,11 @@ class incremental_merkle_tree {
          return {};
       assert(!trees.empty());
       return _get_root(0);
-   };
+   }
+
+   uint64_t num_digests_appended() const {
+      return mask;
+   }
 
 private:
    friend struct fc::reflector<incremental_merkle_tree>;
diff --git a/unittests/merkle_tree_tests.cpp b/unittests/merkle_tree_tests.cpp
index c6e26d5d3f..092a5545ba 100644
--- a/unittests/merkle_tree_tests.cpp
+++ b/unittests/merkle_tree_tests.cpp
@@ -173,8 +173,10 @@ BOOST_AUTO_TEST_CASE(consistency_over_large_range) {
    std::vector<digest_type> digests = create_test_digests(num_digests);
    for (size_t i=1; i<num_digests; ++i) {
       incremental_merkle_tree tree;
-      for (size_t j=0; j<i; ++j)
+      for (size_t j=0; j<i; ++j) {
+         BOOST_CHECK_EQUAL(tree.num_digests_appended(), j);
          tree.append(digests[j]);
+      }
       BOOST_CHECK_EQUAL(calculate_merkle({digests.begin(), digests.begin() + i}), tree.get_root());
    }
 }