diff --git a/src/realm/collection.cpp b/src/realm/collection.cpp
index 73415f8a91d..636c89f6838 100644
--- a/src/realm/collection.cpp
+++ b/src/realm/collection.cpp
@@ -96,8 +96,9 @@ std::pair<std::string, std::string> CollectionBase::get_open_close_strings(size_
 {
     std::string open_str;
     std::string close_str;
-    auto ck = get_col_key();
+    auto collection_type = get_collection_type();
     Table* target_table = get_target_table().unchecked_ptr();
+    auto ck = get_col_key();
     auto type = ck.get_type();
     if (type == col_type_LinkList)
         type = col_type_Link;
@@ -107,29 +108,31 @@ std::pair<std::string, std::string> CollectionBase::get_open_close_strings(size_
 
         if (output_mode == output_mode_xjson_plus) {
             open_str = std::string("{ ") + (is_embedded ? "\"$embedded" : "\"$link");
-            open_str += collection_type_name(ck, true);
+            open_str += collection_type_name(collection_type, true);
             open_str += "\": ";
             close_str += " }";
         }
 
         if ((link_depth_reached && output_mode != output_mode_xjson) || output_mode == output_mode_xjson_plus) {
             open_str += "{ \"table\": \"" + std::string(target_table->get_name()) + "\", ";
-            open_str += ((is_embedded || ck.is_dictionary()) ? "\"value" : "\"key");
-            if (ck.is_collection())
-                open_str += "s";
+            open_str += ((is_embedded || collection_type == CollectionType::Dictionary) ? "\"values" : "\"keys");
             open_str += "\": ";
             close_str += "}";
         }
     }
     else {
         if (output_mode == output_mode_xjson_plus) {
-            if (ck.is_set()) {
-                open_str = "{ \"$set\": ";
-                close_str = " }";
-            }
-            else if (ck.is_dictionary()) {
-                open_str = "{ \"$dictionary\": ";
-                close_str = " }";
+            switch (collection_type) {
+                case CollectionType::List:
+                    break;
+                case CollectionType::Set:
+                    open_str = "{ \"$set\": ";
+                    close_str = " }";
+                    break;
+                case CollectionType::Dictionary:
+                    open_str = "{ \"$dictionary\": ";
+                    close_str = " }";
+                    break;
             }
         }
     }
diff --git a/src/realm/collection.hpp b/src/realm/collection.hpp
index 78a977bb951..04e52c70eac 100644
--- a/src/realm/collection.hpp
+++ b/src/realm/collection.hpp
@@ -90,6 +90,9 @@ class CollectionBase : public Collection {
     /// the internal state of the accessor if it has changed.
     virtual bool has_changed() const noexcept = 0;
 
+    /// Get collection type (set, list, dictionary)
+    virtual CollectionType get_collection_type() const noexcept = 0;
+
     /// Returns true if the accessor is in the attached state. By default, this
     /// checks if the owning object is still valid.
     virtual bool is_attached() const
@@ -154,21 +157,23 @@ class CollectionBase : public Collection {
     std::pair<std::string, std::string> get_open_close_strings(size_t link_depth, JSONOutputMode output_mode) const;
 };
 
-inline std::string_view collection_type_name(ColKey col, bool uppercase = false)
+inline std::string_view collection_type_name(CollectionType col_type, bool uppercase = false)
 {
-    if (col.is_list())
-        return uppercase ? "List" : "list";
-    if (col.is_set())
-        return uppercase ? "Set" : "set";
-    if (col.is_dictionary())
-        return uppercase ? "Dictionary" : "dictionary";
+    switch (col_type) {
+        case CollectionType::List:
+            return uppercase ? "List" : "list";
+        case CollectionType::Set:
+            return uppercase ? "Set" : "set";
+        case CollectionType::Dictionary:
+            return uppercase ? "Dictionary" : "dictionary";
+    }
     return "";
 }
 
 inline void CollectionBase::validate_index(const char* msg, size_t index, size_t size) const
 {
     if (index >= size) {
-        throw OutOfBounds(util::format("%1 on %2 '%3.%4'", msg, collection_type_name(get_col_key()),
+        throw OutOfBounds(util::format("%1 on %2 '%3.%4'", msg, collection_type_name(get_collection_type()),
                                        get_table()->get_class_name(), get_property_name()),
                           index, size);
     }
@@ -382,6 +387,11 @@ class CollectionBaseImpl : public Interface, protected ArrayParent {
         return false;
     }
 
+    CollectionType get_collection_type() const noexcept override
+    {
+        return Interface::s_collection_type;
+    }
+
     void set_owner(const Obj& obj, ColKey ck) override
     {
         m_obj_mem = obj;
@@ -471,7 +481,7 @@ class CollectionBaseImpl : public Interface, protected ArrayParent {
     ref_type get_collection_ref() const noexcept
     {
         try {
-            return m_parent->get_collection_ref(m_index);
+            return m_parent->get_collection_ref(m_index, Interface::s_collection_type);
         }
         catch (const KeyNotFound&) {
             return ref_type(0);
@@ -480,7 +490,7 @@ class CollectionBaseImpl : public Interface, protected ArrayParent {
 
     void set_collection_ref(ref_type ref)
     {
-        m_parent->set_collection_ref(m_index, ref);
+        m_parent->set_collection_ref(m_index, ref, Interface::s_collection_type);
     }
 
     UpdateStatus get_update_status() const noexcept
diff --git a/src/realm/collection_list.cpp b/src/realm/collection_list.cpp
index 1e85974dbf8..1e0f94af623 100644
--- a/src/realm/collection_list.cpp
+++ b/src/realm/collection_list.cpp
@@ -39,7 +39,7 @@ CollectionList::CollectionList(std::shared_ptr<CollectionParent> parent, ColKey
     , m_col_key(col_key)
     , m_top(*m_alloc)
     , m_refs(*m_alloc)
-    , m_key_type(coll_type == CollectionType::List ? type_Int : type_String)
+    , m_coll_type(coll_type)
 {
     m_top.set_parent(this, 0);
     m_refs.set_parent(&m_top, 1);
@@ -51,7 +51,7 @@ CollectionList::CollectionList(CollectionParent* obj, ColKey col_key)
     , m_col_key(col_key)
     , m_top(*m_alloc)
     , m_refs(*m_alloc)
-    , m_key_type(get_table()->get_nested_column_type(col_key, 0) == CollectionType::List ? type_Int : type_String)
+    , m_coll_type(get_table()->get_nested_column_type(col_key, 0))
 {
     m_top.set_parent(this, 0);
     m_refs.set_parent(&m_top, 1);
@@ -61,14 +61,14 @@ CollectionList::~CollectionList() {}
 
 bool CollectionList::init_from_parent(bool allow_create) const
 {
-    auto ref = m_parent->get_collection_ref(m_index);
+    auto ref = m_parent->get_collection_ref(m_index, m_coll_type);
     if ((ref || allow_create) && !m_keys) {
-        switch (m_key_type) {
-            case type_String: {
+        switch (m_coll_type) {
+            case CollectionType::Dictionary: {
                 m_keys.reset(new BPlusTree<StringData>(*m_alloc));
                 break;
             }
-            case type_Int: {
+            case CollectionType::List: {
                 m_keys.reset(new BPlusTree<Int>(*m_alloc));
                 break;
             }
@@ -170,19 +170,19 @@ bool CollectionList::update_if_needed() const
 
 ref_type CollectionList::get_child_ref(size_t) const noexcept
 {
-    return m_parent->get_collection_ref(m_col_key);
+    return m_parent->get_collection_ref(m_col_key, m_coll_type);
 }
 
 void CollectionList::update_child_ref(size_t, ref_type ref)
 {
-    m_parent->set_collection_ref(m_index, ref);
+    m_parent->set_collection_ref(m_index, ref, m_coll_type);
 }
 
 CollectionBasePtr CollectionList::insert_collection(size_t ndx)
 {
     REALM_ASSERT(get_table()->get_nesting_levels(m_col_key) == m_level);
     ensure_created();
-    REALM_ASSERT(m_key_type == type_Int);
+    REALM_ASSERT(m_coll_type == CollectionType::List);
     auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
     int64_t key = 0;
     if (auto max = bptree_maximum(*int_keys, nullptr)) {
@@ -202,7 +202,7 @@ CollectionBasePtr CollectionList::insert_collection(StringData key)
 {
     REALM_ASSERT(get_table()->get_nesting_levels(m_col_key) == m_level);
     ensure_created();
-    REALM_ASSERT(m_key_type == type_String);
+    REALM_ASSERT(m_coll_type == CollectionType::Dictionary);
     auto string_keys = static_cast<BPlusTree<String>*>(m_keys.get());
     StringData actual;
     IteratorAdapter help(string_keys);
@@ -231,7 +231,7 @@ CollectionBasePtr CollectionList::get_collection(size_t ndx) const
     if (ndx >= sz) {
         throw OutOfBounds("CollectionList::get_collection_ptr()", ndx, sz);
     }
-    if (m_key_type == type_Int) {
+    if (m_coll_type == CollectionType::List) {
         auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
         index = int_keys->get(ndx);
     }
@@ -246,7 +246,7 @@ CollectionBasePtr CollectionList::get_collection(size_t ndx) const
 CollectionListPtr CollectionList::insert_collection_list(size_t ndx)
 {
     ensure_created();
-    REALM_ASSERT(m_key_type == type_Int);
+    REALM_ASSERT(m_coll_type == CollectionType::List);
     auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
     int64_t key = 0;
     if (auto max = bptree_maximum(*int_keys, nullptr)) {
@@ -263,7 +263,7 @@ CollectionListPtr CollectionList::insert_collection_list(size_t ndx)
 CollectionListPtr CollectionList::insert_collection_list(StringData key)
 {
     ensure_created();
-    REALM_ASSERT(m_key_type == type_String);
+    REALM_ASSERT(m_coll_type == CollectionType::Dictionary);
     auto string_keys = static_cast<BPlusTree<String>*>(m_keys.get());
     StringData actual;
     IteratorAdapter help(string_keys);
@@ -289,7 +289,7 @@ CollectionListPtr CollectionList::get_collection_list(size_t ndx) const
     if (ndx >= sz) {
         throw OutOfBounds("CollectionList::get_collection_ptr()", ndx, sz);
     }
-    if (m_key_type == type_Int) {
+    if (m_coll_type == CollectionType::List) {
         auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
         index = int_keys->get(ndx);
     }
@@ -303,7 +303,7 @@ CollectionListPtr CollectionList::get_collection_list(size_t ndx) const
 
 void CollectionList::remove(size_t ndx)
 {
-    REALM_ASSERT(m_key_type == type_Int);
+    REALM_ASSERT(m_coll_type == CollectionType::List);
     auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
     const auto sz = int_keys->size();
     if (ndx >= sz) {
@@ -331,7 +331,7 @@ void CollectionList::remove(size_t ndx)
 
 void CollectionList::remove(StringData key)
 {
-    REALM_ASSERT(m_key_type == type_String);
+    REALM_ASSERT(m_coll_type == CollectionType::Dictionary);
     auto string_keys = static_cast<BPlusTree<String>*>(m_keys.get());
     IteratorAdapter help(string_keys);
     auto it = std::lower_bound(help.begin(), help.end(), key);
@@ -347,10 +347,10 @@ void CollectionList::remove(StringData key)
     bump_content_version();
 }
 
-ref_type CollectionList::get_collection_ref(Index index) const noexcept
+ref_type CollectionList::get_collection_ref(Index index, CollectionType) const noexcept
 {
     size_t ndx;
-    if (m_key_type == type_Int) {
+    if (m_coll_type == CollectionType::List) {
         auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
         ndx = int_keys->find_first(mpark::get<int64_t>(index));
     }
@@ -361,10 +361,10 @@ ref_type CollectionList::get_collection_ref(Index index) const noexcept
     return ndx == realm::not_found ? 0 : m_refs.get(ndx);
 }
 
-void CollectionList::set_collection_ref(Index index, ref_type ref)
+void CollectionList::set_collection_ref(Index index, ref_type ref, CollectionType)
 {
     size_t ndx;
-    if (m_key_type == type_Int) {
+    if (m_coll_type == CollectionType::List) {
         auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
         ndx = int_keys->find_first(mpark::get<int64_t>(index));
     }
@@ -380,7 +380,7 @@ void CollectionList::set_collection_ref(Index index, ref_type ref)
 
 auto CollectionList::get_index(size_t ndx) const noexcept -> Index
 {
-    if (m_key_type == type_Int) {
+    if (m_coll_type == CollectionType::List) {
         auto int_keys = static_cast<BPlusTree<Int>*>(m_keys.get());
         return int_keys->get(ndx);
     }
@@ -431,7 +431,7 @@ void CollectionList::to_json(std::ostream& out, size_t link_depth, JSONOutputMod
                              util::FunctionRef<void(const Mixed&)> fn) const
 {
     bool is_leaf = m_level == get_table()->get_nesting_levels(m_col_key);
-    bool is_dictionary = m_key_type == type_String;
+    bool is_dictionary = m_coll_type == CollectionType::Dictionary;
     auto sz = size();
     auto string_keys = static_cast<BPlusTree<String>*>(m_keys.get());
 
diff --git a/src/realm/collection_list.hpp b/src/realm/collection_list.hpp
index 566445bc64c..1c4029ee666 100644
--- a/src/realm/collection_list.hpp
+++ b/src/realm/collection_list.hpp
@@ -76,8 +76,8 @@ class CollectionList final : public Collection,
 
     Index get_index(size_t ndx) const noexcept;
 
-    ref_type get_collection_ref(Index index) const noexcept final;
-    void set_collection_ref(Index index, ref_type ref) final;
+    ref_type get_collection_ref(Index index, CollectionType) const noexcept final;
+    void set_collection_ref(Index index, ref_type ref, CollectionType) final;
 
     // If this list is at the outermost nesting level, use these functions to
     // get the leaf collections
@@ -112,7 +112,7 @@ class CollectionList final : public Collection,
     mutable Array m_top;
     mutable std::unique_ptr<BPlusTreeBase> m_keys;
     mutable BPlusTree<ref_type> m_refs;
-    DataType m_key_type;
+    CollectionType m_coll_type;
     mutable uint_fast64_t m_content_version = 0;
 
 
diff --git a/src/realm/collection_parent.hpp b/src/realm/collection_parent.hpp
index 9587c2e7abe..29d560fa419 100644
--- a/src/realm/collection_parent.hpp
+++ b/src/realm/collection_parent.hpp
@@ -99,9 +99,9 @@ class CollectionParent {
     /// Get owning object
     virtual const Obj& get_object() const noexcept = 0;
     /// Get the top ref from pareht
-    virtual ref_type get_collection_ref(Index) const noexcept = 0;
-    /// Set the top ref from pareht
-    virtual void set_collection_ref(Index, ref_type ref) = 0;
+    virtual ref_type get_collection_ref(Index, CollectionType) const = 0;
+    /// Set the top ref in parent
+    virtual void set_collection_ref(Index, ref_type ref, CollectionType) = 0;
 
     // Used when inserting a new link. You will not remove existing links in this process
     void set_backlink(ColKey col_key, ObjLink new_link) const;
@@ -145,11 +145,11 @@ class DummyParent : public CollectionParent {
         return true;
     }
     const Obj& get_object() const noexcept final;
-    ref_type get_collection_ref(Index) const noexcept final
+    ref_type get_collection_ref(Index, CollectionType) const final
     {
         return m_ref;
     }
-    void set_collection_ref(Index, ref_type) {}
+    void set_collection_ref(Index, ref_type, CollectionType) {}
 };
 
 } // namespace realm
diff --git a/src/realm/dictionary.hpp b/src/realm/dictionary.hpp
index 188fc2bbca6..eb39706972b 100644
--- a/src/realm/dictionary.hpp
+++ b/src/realm/dictionary.hpp
@@ -394,6 +394,10 @@ class DictionaryLinkValues final : public ObjCollectionBase<CollectionBase> {
     {
         return m_source.has_changed();
     }
+    CollectionType get_collection_type() const noexcept override
+    {
+        return CollectionType::List;
+    }
 
     // Overrides of ObjCollectionBase:
     UpdateStatus do_update_if_needed() const final
diff --git a/src/realm/list.hpp b/src/realm/list.hpp
index 887f2ccc50a..4ce9ec243e8 100644
--- a/src/realm/list.hpp
+++ b/src/realm/list.hpp
@@ -68,6 +68,7 @@ class LstBase : public CollectionBase {
     virtual void swap(size_t ndx1, size_t ndx2) = 0;
 
 protected:
+    static constexpr CollectionType s_collection_type = CollectionType::List;
     void swap_repl(Replication* repl, size_t ndx1, size_t ndx2) const;
 };
 
@@ -399,6 +400,10 @@ class LnkLst final : public ObjCollectionBase<LstBase> {
     const Obj& get_obj() const noexcept final;
     bool has_changed() const noexcept final;
     ColKey get_col_key() const noexcept final;
+    CollectionType get_collection_type() const noexcept override
+    {
+        return CollectionType::List;
+    }
 
     // Overriding members of LstBase:
     std::unique_ptr<LstBase> clone() const override
diff --git a/src/realm/obj.cpp b/src/realm/obj.cpp
index d03927e576b..fb8f9249a96 100644
--- a/src/realm/obj.cpp
+++ b/src/realm/obj.cpp
@@ -1658,6 +1658,24 @@ void Obj::set_int(ColKey col_key, int64_t value)
     sync(fields);
 }
 
+void Obj::set_ref(ColKey col_key, ref_type value, CollectionType type)
+{
+    update_if_needed();
+
+    ColKey::Idx col_ndx = col_key.get_index();
+    Allocator& alloc = get_alloc();
+    alloc.bump_content_version();
+    Array fallback(alloc);
+    Array& fields = get_tree_top()->get_fields_accessor(fallback, m_mem);
+    REALM_ASSERT(col_ndx.val + 1 < fields.size());
+    ArrayMixed values(alloc);
+    values.set_parent(&fields, col_ndx.val + 1);
+    values.init_from_parent();
+    values.set(m_row_ndx, Mixed(value, type));
+
+    sync(fields);
+}
+
 void Obj::add_backlink(ColKey backlink_col_key, ObjKey origin_key)
 {
     ColKey::Idx backlink_col_ndx = backlink_col_key.get_index();
@@ -2262,14 +2280,31 @@ ref_type Obj::Internal::get_ref(const Obj& obj, ColKey col_key)
     return to_ref(obj._get<int64_t>(col_key.get_index()));
 }
 
-ref_type Obj::get_collection_ref(Index index) const noexcept
+ref_type Obj::get_collection_ref(Index index, CollectionType type) const
 {
-    return to_ref(_get<int64_t>(mpark::get<ColKey>(index).get_index()));
+    ColKey col_key = mpark::get<ColKey>(index);
+    if (col_key.is_collection()) {
+        return to_ref(_get<int64_t>(col_key.get_index()));
+    }
+    if (col_key.get_type() == col_type_Mixed) {
+        auto val = _get<Mixed>(col_key.get_index());
+        if (val.is_null() || !val.is_type(DataType(int(type)))) {
+            throw IllegalOperation("Not proper collection type");
+        }
+        return val.get_ref();
+    }
+    return 0;
 }
 
-void Obj::set_collection_ref(Index index, ref_type ref)
+void Obj::set_collection_ref(Index index, ref_type ref, CollectionType type)
 {
-    set_int(mpark::get<ColKey>(index), from_ref(ref));
+    ColKey col_key = mpark::get<ColKey>(index);
+    if (col_key.is_collection()) {
+        set_int(col_key, from_ref(ref));
+        return;
+    }
+    REALM_ASSERT(col_key.get_type() == col_type_Mixed);
+    set_ref(col_key, ref, type);
 }
 
 } // namespace realm
diff --git a/src/realm/obj.hpp b/src/realm/obj.hpp
index 7b0ffa8a293..45471b74d03 100644
--- a/src/realm/obj.hpp
+++ b/src/realm/obj.hpp
@@ -83,8 +83,8 @@ class Obj : public CollectionParent {
     {
         return *this;
     }
-    ref_type get_collection_ref(Index index) const noexcept final;
-    void set_collection_ref(Index index, ref_type ref) final;
+    ref_type get_collection_ref(Index, CollectionType) const final;
+    void set_collection_ref(Index, ref_type, CollectionType) final;
 
     // Operator overloads
     bool operator==(const Obj& other) const;
@@ -402,6 +402,7 @@ class Obj : public CollectionParent {
     }
 
     void set_int(ColKey col_key, int64_t value);
+    void set_ref(ColKey col_key, ref_type value, CollectionType type);
     void add_backlink(ColKey backlink_col, ObjKey origin_key);
     bool remove_one_backlink(ColKey backlink_col, ObjKey origin_key);
     void nullify_link(ColKey origin_col, ObjLink target_key) &&;
diff --git a/src/realm/object-store/dictionary.cpp b/src/realm/object-store/dictionary.cpp
index efed961ae9e..102008f074f 100644
--- a/src/realm/object-store/dictionary.cpp
+++ b/src/realm/object-store/dictionary.cpp
@@ -116,6 +116,10 @@ class DictionaryKeyAdapter : public CollectionBase {
     {
         m_dictionary->set_owner(std::move(parent), index);
     }
+    CollectionType get_collection_type() const noexcept override
+    {
+        return CollectionType::List;
+    }
 
 private:
     std::shared_ptr<Dictionary> m_dictionary;
diff --git a/src/realm/object-store/results.cpp b/src/realm/object-store/results.cpp
index eaa94e2245c..30509858622 100644
--- a/src/realm/object-store/results.cpp
+++ b/src/realm/object-store/results.cpp
@@ -34,7 +34,8 @@ namespace realm {
 [[noreturn]] static void unsupported_operation(ColKey column, Table const& table, const char* operation)
 {
     auto type = ObjectSchema::from_core_type(column);
-    std::string_view collection_type = column.is_collection() ? collection_type_name(column) : "property";
+    std::string_view collection_type =
+        column.is_collection() ? collection_type_name(table.get_collection_type(column, 0)) : "property";
     const char* column_type = string_for_property_type(type & ~PropertyType::Collection);
     throw IllegalOperation(util::format("Operation '%1' not supported for %2%3 %4 '%5.%6'", operation, column_type,
                                         column.is_nullable() ? "?" : "", collection_type, table.get_class_name(),
diff --git a/src/realm/set.hpp b/src/realm/set.hpp
index 68a5b7d1884..cd6a14f3f84 100644
--- a/src/realm/set.hpp
+++ b/src/realm/set.hpp
@@ -39,6 +39,8 @@ class SetBase : public CollectionBase {
     virtual std::pair<size_t, bool> erase_any(Mixed value) = 0;
 
 protected:
+    static constexpr CollectionType s_collection_type = CollectionType::Set;
+
     void insert_repl(Replication* repl, size_t index, Mixed value) const;
     void erase_repl(Replication* repl, size_t index, Mixed value) const;
     void clear_repl(Replication* repl) const;
@@ -332,6 +334,10 @@ class LnkSet final : public ObjCollectionBase<SetBase> {
     bool is_attached() const final;
     bool has_changed() const noexcept final;
     ColKey get_col_key() const noexcept final;
+    CollectionType get_collection_type() const noexcept override
+    {
+        return CollectionType::Set;
+    }
 
     // Overriding members of SetBase:
     SetBasePtr clone() const override