diff --git a/include/boost/unordered/detail/implementation.hpp b/include/boost/unordered/detail/implementation.hpp
index 6774ce00..f006a03b 100644
--- a/include/boost/unordered/detail/implementation.hpp
+++ b/include/boost/unordered/detail/implementation.hpp
@@ -3540,45 +3540,26 @@ struct table : boost::unordered::detail::functions<typename Types::hasher,
             (boost::is_same<node, typename other_table::node>::value));
         BOOST_ASSERT(this->node_alloc() == other.node_alloc());
 
-        if (!other.size_) {
-            return;
-        }
+        if (other.size_) {
+            link_pointer prev = other.get_previous_start();
 
-        link_pointer prev = other.get_previous_start();
-        node_pointer n = other_table::next_node(prev);
-        while (n) {
-            const_key_type& k = this->get_key(n);
-            std::size_t key_hash = this->hash(k);
-            node_pointer pos = this->find_node(key_hash, k);
+            while (prev->next_) {
+                node_pointer n = other_table::next_node(prev);
+                const_key_type& k = this->get_key(n);
+                std::size_t key_hash = this->hash(k);
+                node_pointer pos = this->find_node(key_hash, k);
 
-            if (pos) {
-                prev = n;
-                n = other_table::next_node(prev);
-            } else {
-                this->reserve_for_insert(this->size_ + 1);
-
-                prev->next_ = n->next_;
-                --other.size_;
-                other.fix_bucket(other.node_bucket(n), prev);
-                this->add_node_unique(n, key_hash);
-                n = other_table::next_node(prev);
-
-                // If the next node was from the same group, it's now
-                // the first node in the group.
-                if (n && !n->is_first_in_group()) {
-                    n->set_first_in_group();
+                if (pos) {
                     prev = n;
-                    n = other_table::next_node(prev);
-                }
-            }
-
-            // Skip over rest of group of nodes with equivalent keys,
-            // as we know there's already one in the container.
-            while (n && !n->is_first_in_group()) {
-                prev = n;
-                n = other_table::next_node(prev);
-                if (!n) {
-                    return;
+                } else {
+                    this->reserve_for_insert(this->size_ + 1);
+                    prev->next_ = n->next_;
+                    if (prev->next_ && n->is_first_in_group()) {
+                        next_node(prev)->set_first_in_group();
+                    }
+                    --other.size_;
+                    other.fix_bucket(other.node_bucket(n), prev);
+                    this->add_node_unique(n, key_hash);
                 }
             }
         }
diff --git a/test/unordered/merge_tests.cpp b/test/unordered/merge_tests.cpp
index b848e4f3..59b0b4a5 100644
--- a/test/unordered/merge_tests.cpp
+++ b/test/unordered/merge_tests.cpp
@@ -170,7 +170,8 @@ void merge_into_empty_test(X*, test::random_generator generator)
 }
 
 template <class X1, class X2>
-void merge_into_unique_keys_test(X1*, X2*, test::random_generator generator)
+void merge_into_unique_keys_test(
+    X1*, X2*, int hash_equal1, int hash_equal2, test::random_generator generator)
 {
     test::check_instances check_;
 
@@ -179,8 +180,10 @@ void merge_into_unique_keys_test(X1*, X2*, test::random_generator generator)
     v1.insert(v2.begin(), boost::next(v2.begin(), 100));
     v2.insert(v1.begin(), boost::next(v1.begin(), 100));
 
-    X1 x1(v1.begin(), v1.end());
-    X2 x2(v2.begin(), v2.end());
+    X1 x1(v1.begin(), v1.end(), 0, test::hash(hash_equal1),
+        test::equal_to(hash_equal1));
+    X2 x2(v2.begin(), v2.end(), 0, test::hash(hash_equal2),
+        test::equal_to(hash_equal2));
     x1.merge(x2);
 
     test::ordered<X1> tracker1 = test::create_ordered(x1);
@@ -203,7 +206,8 @@ void merge_into_unique_keys_test(X1*, X2*, test::random_generator generator)
 }
 
 template <class X1, class X2>
-void merge_into_equiv_keys_test(X1*, X2*, test::random_generator generator)
+void merge_into_equiv_keys_test(
+    X1*, X2*, int hash_equal1, int hash_equal2, test::random_generator generator)
 {
     test::check_instances check_;
 
@@ -212,16 +216,21 @@ void merge_into_equiv_keys_test(X1*, X2*, test::random_generator generator)
     v1.insert(v2.begin(), boost::next(v2.begin(), 100));
     v2.insert(v1.begin(), boost::next(v1.begin(), 100));
 
-    X1 x1(v1.begin(), v1.end());
-    X2 x2(v2.begin(), v2.end());
+    X1 x1(v1.begin(), v1.end(), 0, test::hash(hash_equal1),
+        test::equal_to(hash_equal1));
+    X2 x2(v2.begin(), v2.end(), 0, test::hash(hash_equal2),
+        test::equal_to(hash_equal2));
     x1.merge(x2);
 
     test::ordered<X1> tracker1 = test::create_ordered(x1);
+    test::ordered<X2> tracker2 = test::create_ordered(x2);
     tracker1.insert(v1.begin(), v1.end());
-    tracker1.insert(v2.begin(), v2.end());
+    tracker2.insert(v2.begin(), v2.end());
+    tracker1.insert(tracker2.begin(), tracker2.end());
+    tracker2.clear();
 
     tracker1.compare(x1);
-    BOOST_TEST(x2.empty());
+    tracker2.compare(x2);
     test::check_equivalent_keys(x1);
     test::check_equivalent_keys(x2);
 }
@@ -231,8 +240,8 @@ boost::unordered_set<test::movable, test::hash, test::equal_to,
 boost::unordered_multiset<test::movable, test::hash, test::equal_to,
     std::allocator<test::movable> >* test_multiset_std_alloc;
 
-boost::unordered_map<test::object, test::object, test::hash,
-    test::equal_to, std::allocator<test::object> >* test_map_std_alloc;
+boost::unordered_map<test::object, test::object, test::hash, test::equal_to,
+    std::allocator<test::object> >* test_map_std_alloc;
 boost::unordered_multimap<test::object, test::object, test::hash,
     test::equal_to, std::allocator<test::object> >* test_multimap_std_alloc;
 
@@ -283,35 +292,51 @@ UNORDERED_TEST(merge_into_empty_test,
 UNORDERED_TEST(merge_into_unique_keys_test,
     ((test_set_std_alloc))
     ((test_set_std_alloc)(test_multiset_std_alloc))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 UNORDERED_TEST(merge_into_unique_keys_test,
     ((test_map_std_alloc))
     ((test_map_std_alloc)(test_multimap_std_alloc))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 UNORDERED_TEST(merge_into_unique_keys_test,
     ((test_set))
     ((test_set)(test_multiset))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 UNORDERED_TEST(merge_into_unique_keys_test,
     ((test_map))
     ((test_map)(test_multimap))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 
 UNORDERED_TEST(merge_into_equiv_keys_test,
     ((test_multiset_std_alloc))
     ((test_set_std_alloc)(test_multiset_std_alloc))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 UNORDERED_TEST(merge_into_equiv_keys_test,
     ((test_multimap_std_alloc))
     ((test_map_std_alloc)(test_multimap_std_alloc))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 UNORDERED_TEST(merge_into_equiv_keys_test,
     ((test_multiset))
     ((test_set)(test_multiset))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 UNORDERED_TEST(merge_into_equiv_keys_test,
     ((test_multimap))
     ((test_map)(test_multimap))
+    ((0)(1)(2))
+    ((0)(1)(2))
     ((default_generator)(generate_collisions)))
 // clang-format on