diff --git a/hnswlib/hnswalg.h b/hnswlib/hnswalg.h
index cc767847..8adaa591 100644
--- a/hnswlib/hnswalg.h
+++ b/hnswlib/hnswalg.h
@@ -1703,6 +1703,9 @@ namespace hnswlib
                 // Do nothing for the first element
                 enterpoint_node_ = 0;
                 maxlevel_ = curlevel;
+
+                // mark cur_c as dirty
+                markElementToPersist(cur_c);
             }
 
             // Releasing lock for the maximum level
diff --git a/tests/cpp/persistent_test.cpp b/tests/cpp/persistent_test.cpp
index 666999b5..d93e66af 100644
--- a/tests/cpp/persistent_test.cpp
+++ b/tests/cpp/persistent_test.cpp
@@ -300,6 +300,231 @@ namespace
     }
 }
 
+void test_persist_empty() {
+    int d = 1;
+    idx_t n = 0;
+    idx_t nq = 1;
+
+    std::vector<float> data(n * d);
+    std::vector<float> query(nq * d);
+    std::mt19937 rng;
+    rng.seed(47);
+    std::uniform_real_distribution<> distrib;
+
+    for (idx_t i = 0; i < n * d; i++)
+    {
+        data[i] = distrib(rng);
+    }
+    for (idx_t i = 0; i < nq * d; ++i)
+    {
+        query[i] = distrib(rng);
+    }
+
+    hnswlib::InnerProductSpace space(d);
+    hnswlib::HierarchicalNSW<float> *alg_hnsw = new hnswlib::HierarchicalNSW<float>(&space, n, 16, 200, 100, false, false, true, ".");
+
+    alg_hnsw->persistDirty();
+
+    hnswlib::HierarchicalNSW<float> *alg_hnsw2 = new hnswlib::HierarchicalNSW<float>(&space, ".", false, n, false, false, true);
+    // query and expect no result
+    std::priority_queue<std::pair<float, idx_t>> result = alg_hnsw2->searchKnn(query.data(), 10);
+    assert(result.size() == 0);
+}
+
+void test_persist_size(int n) {
+    int d = 1;
+    idx_t nq = 1;
+    size_t k = 10;
+
+    std::vector<float> data(n * d);
+    std::vector<float> query(nq * d);
+    std::mt19937 rng;
+    rng.seed(47);
+    std::uniform_real_distribution<> distrib;
+
+
+    for (idx_t i = 0; i < n * d; i++)
+    {
+        data[i] = distrib(rng);
+    }
+    for (idx_t i = 0; i < nq * d; ++i)
+    {
+        query[i] = distrib(rng);
+    }
+
+    hnswlib::InnerProductSpace space(d);
+    hnswlib::HierarchicalNSW<float> *alg_hnsw = new hnswlib::HierarchicalNSW<float>(&space, n, 16, 200, 100, false, false, true, ".");
+
+    for (size_t i = 0; i < n; i++)
+    {
+        alg_hnsw->addPoint(data.data() + d * i, i);        
+        alg_hnsw->persistDirty();
+    }
+    alg_hnsw->persistDirty();
+
+    hnswlib::HierarchicalNSW<float> *alg_hnsw2 = new hnswlib::HierarchicalNSW<float>(&space, ".", false, n, false, false, true);
+
+
+    // Check that all data is the same
+    for (size_t i = 0; i < n; i++)
+    {
+        std::vector<float> actual = alg_hnsw2->template getDataByLabel<float>(i);
+        for (size_t j = 0; j < d; j++)
+        {
+            // Check that abs difference is less than 1e-6
+            if (!(std::abs(actual[j] - data[d * i + j]) < 1e-6))
+            {
+                std::cout << "actual: " << actual[j] << " expected: " << data[d * i + j] << std::endl;
+            }
+            assert(std::abs(actual[j] - data[d * i + j]) < 1e-6);
+        }
+    }
+
+    // Compare to in-memory index
+    for (size_t j = 0; j < nq; ++j)
+    {
+        const void *p = query.data() + j * d;
+        auto gd = alg_hnsw->searchKnn(p, k);
+        auto res = alg_hnsw2->searchKnn(p, k);
+        assert(gd.size() == res.size());
+        int missed = 0;
+        for (size_t i = 0; i < gd.size(); i++)
+        {
+            assert(std::abs(gd.top().first - res.top().first) < 1e-6);
+            assert(gd.top().second == res.top().second);
+            gd.pop();
+            res.pop();
+        }
+    }    
+}
+
+void test_persist_then_delete_size(int n) {
+    int d = 1;
+    idx_t nq = 1;
+    size_t k = 10;
+
+    std::vector<float> data(n * d);
+    std::vector<float> query(nq * d);
+    std::mt19937 rng;
+    rng.seed(47);
+    std::uniform_real_distribution<> distrib;
+
+    for (idx_t i = 0; i < n * d; i++)
+    {
+        data[i] = distrib(rng);
+    }
+    for (idx_t i = 0; i < nq * d; ++i)
+    {
+        query[i] = distrib(rng);
+    }
+
+    hnswlib::InnerProductSpace space(d);
+    hnswlib::HierarchicalNSW<float> *alg_hnsw = new hnswlib::HierarchicalNSW<float>(&space, n, 16, 200, 100, false, false, true, ".");
+
+    for (size_t i = 0; i < n; i++)
+    {
+        alg_hnsw->addPoint(data.data() + d * i, i); 
+        alg_hnsw->persistDirty();
+    }
+    alg_hnsw->persistDirty();
+
+    // Delete the inserted data and then persist
+    for (size_t i = 0; i < n; i++)
+    {
+        alg_hnsw->markDelete(i);
+        alg_hnsw->persistDirty();
+    }
+    alg_hnsw->persistDirty();
+
+    hnswlib::HierarchicalNSW<float> *alg_hnsw2 = new hnswlib::HierarchicalNSW<float>(&space, ".", false, n, false, false, true);
+
+    // query and expect no result
+    std::priority_queue<std::pair<float, idx_t>> result = alg_hnsw2->searchKnn(query.data(), 10);
+    assert(result.size() == 0);
+}
+
+void test_persist_size_then_add(int n, int second_n) {
+    int d = 1536;
+    idx_t nq = 1;
+    size_t k = 10;
+
+    std::vector<float> data(n * d);
+    std::vector<float> query(nq * d);
+    std::mt19937 rng;
+    rng.seed(47);
+    std::uniform_real_distribution<> distrib;
+
+
+    for (idx_t i = 0; i < n * d; i++)
+    {
+        data[i] = distrib(rng);
+    }
+    for (idx_t i = 0; i < nq * d; ++i)
+    {
+        query[i] = distrib(rng);
+    }
+
+    hnswlib::InnerProductSpace space(d);
+    hnswlib::HierarchicalNSW<float> *alg_hnsw = new hnswlib::HierarchicalNSW<float>(&space, n, 16, 200, 100, false, false, true, ".");
+
+    for (size_t i = 0; i < n; i++)
+    {
+        alg_hnsw->addPoint(data.data() + d * i, i);        
+        alg_hnsw->persistDirty();
+    }
+    alg_hnsw->persistDirty();
+
+    hnswlib::HierarchicalNSW<float> *alg_hnsw2 = new hnswlib::HierarchicalNSW<float>(&space, ".", false, n + second_n, false, false, true);
+
+    std::vector<float> data2(second_n * d);
+    for (idx_t i = 0; i < second_n * d; i++)
+    {
+        data2[i] = distrib(rng);
+    }
+
+    for (size_t i = n; i < n + second_n; i++)
+    {
+        alg_hnsw2->addPoint(data2.data() + d * (i - n), i);        
+        alg_hnsw2->persistDirty();
+    }
+    alg_hnsw2->persistDirty();
+
+    // Load alg_hnsw3
+    hnswlib::HierarchicalNSW<float> *alg_hnsw3 = new hnswlib::HierarchicalNSW<float>(&space, ".", false, n + second_n, false, false, true);
+    
+    // Check that all data is the same
+    for (size_t i = 0; i < n + second_n; i++)
+    {
+        std::vector<float> actual = alg_hnsw3->template getDataByLabel<float>(i);
+        for (size_t j = 0; j < d; j++)
+        {
+            // Check that abs difference is less than 1e-6
+            if (!(std::abs(actual[j] - (i < n ? data[d * i + j] : data2[d * (i - n) + j])) < 1e-6))
+            {
+                std::cout << "actual: " << actual[j] << " expected: " << (i < n ? data[d * i + j] : data2[d * (i - n) + j]) << std::endl;
+            }
+            assert(std::abs(actual[j] - (i < n ? data[d * i + j] : data2[d * (i - n) + j]) < 1e-6));
+        }
+    }
+
+    // Compare to in-memory index
+    for (size_t j = 0; j < nq; ++j)
+    {
+        const void *p = query.data() + j * d;
+        auto gd = alg_hnsw2->searchKnn(p, k);
+        auto res = alg_hnsw3->searchKnn(p, k);
+        assert(gd.size() == res.size());
+        int missed = 0;
+        for (size_t i = 0; i < gd.size(); i++)
+        {
+            assert(std::abs(gd.top().first - res.top().first) < 1e-6);
+            assert(gd.top().second == res.top().second);
+            gd.pop();
+            res.pop();
+        }
+    }
+}
+
 int main()
 {
     std::cout << "Testing ..." << std::endl;
@@ -311,5 +536,25 @@ int main()
     std::cout << "Test testAddUpdatePersistentIndex ok" << std::endl;
     testDeletePersistentIndex();
     std::cout << "Test testDeletePersistentIndex ok" << std::endl;
+    test_persist_empty();
+    std::cout << "Test test_persist_empty ok" << std::endl;
+    test_persist_size(1);
+    std::cout << "Test test_persist_size(1) ok" << std::endl;
+    test_persist_size(2);
+    std::cout << "Test test_persist_size(2) ok" << std::endl;
+    test_persist_size(3);
+    std::cout << "Test test_persist_size(3) ok" << std::endl;
+    test_persist_then_delete_size(1);
+    std::cout << "Test test_persist_then_delete_size(1) ok" << std::endl;
+    test_persist_then_delete_size(2);
+    std::cout << "Test test_persist_then_delete_size(2) ok" << std::endl;
+    test_persist_size_then_add(1, 1);
+    std::cout << "Test test_persist_size_then_add(1, 1) ok" << std::endl;
+    test_persist_size_then_add(2, 1);
+    std::cout << "Test test_persist_size_then_add(2, 1) ok" << std::endl;
+    test_persist_size_then_add(1, 1000);
+    std::cout << "Test test_persist_size_then_add(1, 1000) ok" << std::endl;
+    test_persist_size_then_add(2, 1000);
+    std::cout << "Test test_persist_size_then_add(2, 1000) ok" << std::endl;
     return 0;
 }