diff --git a/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.cpp b/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.cpp
index a5dfedc0571..e6dc7c7b731 100644
--- a/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.cpp
+++ b/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.cpp
@@ -119,6 +119,17 @@ void CustomAllocator::PrepareForGC() noexcept {
     extraObjectPage_ = nullptr;
 }
 
+// static
+size_t CustomAllocator::GetAllocatedHeapSize(ObjHeader* object) noexcept {
+    RuntimeAssert(object->heap(), "Object must be a heap object");
+    const auto* typeInfo = object->type_info();
+    if (typeInfo->IsArray()) {
+        return ArrayAllocatedDataSize(typeInfo, object->array()->count_);
+    } else {
+        return ObjectAllocatedDataSize(typeInfo);
+    }
+}
+
 uint8_t* CustomAllocator::Allocate(uint64_t size) noexcept {
     gcScheduler_.OnSafePointAllocation(size);
     CustomAllocDebug("CustomAllocator::Allocate(%" PRIu64 ")", size);
diff --git a/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.hpp b/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.hpp
index 5b058ca013a..cd0a73673a4 100644
--- a/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.hpp
+++ b/kotlin-native/runtime/src/custom_alloc/cpp/CustomAllocator.hpp
@@ -34,6 +34,8 @@ public:
 
     void PrepareForGC() noexcept;
 
+    static size_t GetAllocatedHeapSize(ObjHeader* object) noexcept;
+
 private:
     uint8_t* Allocate(uint64_t cellCount) noexcept;
     uint8_t* AllocateInSingleObjectPage(uint64_t cellCount) noexcept;
diff --git a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.cpp b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.cpp
index a51b4b2c68c..4fc03d5d0e6 100644
--- a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.cpp
+++ b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.cpp
@@ -105,13 +105,14 @@ NO_EXTERNAL_CALLS_CHECK void gc::ConcurrentMarkAndSweep::ThreadData::OnSuspendFo
     gc::Mark<internal::MarkTraits>(handle, markQueue);
 }
 
+#ifndef CUSTOM_ALLOCATOR
 gc::ConcurrentMarkAndSweep::ConcurrentMarkAndSweep(
         mm::ObjectFactory<ConcurrentMarkAndSweep>& objectFactory, GCScheduler& gcScheduler) noexcept :
-#ifndef CUSTOM_ALLOCATOR
     objectFactory_(objectFactory),
     gcScheduler_(gcScheduler),
     finalizerProcessor_(std_support::make_unique<FinalizerProcessor>([this](int64_t epoch) {
 #else
+gc::ConcurrentMarkAndSweep::ConcurrentMarkAndSweep(GCScheduler& gcScheduler) noexcept :
     gcScheduler_(gcScheduler), finalizerProcessor_(std_support::make_unique<alloc::CustomFinalizerProcessor>([this](int64_t epoch) {
 #endif
         GCHandle::getByEpoch(epoch).finalizersDone();
diff --git a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.hpp b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.hpp
index e26d9b972a4..c2bc62ed568 100644
--- a/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.hpp
+++ b/kotlin-native/runtime/src/gc/cms/cpp/ConcurrentMarkAndSweep.hpp
@@ -108,7 +108,11 @@ public:
 
     using Allocator = ThreadData::Allocator;
 
+#ifdef CUSTOM_ALLOCATOR
+    explicit ConcurrentMarkAndSweep(GCScheduler& scheduler) noexcept;
+#else
     ConcurrentMarkAndSweep(mm::ObjectFactory<ConcurrentMarkAndSweep>& objectFactory, GCScheduler& scheduler) noexcept;
+#endif
     ~ConcurrentMarkAndSweep();
 
     void StartFinalizerThreadIfNeeded() noexcept;
diff --git a/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.cpp b/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.cpp
index 72e6c82715f..049e173e819 100644
--- a/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.cpp
+++ b/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.cpp
@@ -88,21 +88,41 @@ gc::GC::~GC() = default;
 
 // static
 size_t gc::GC::GetAllocatedHeapSize(ObjHeader* object) noexcept {
+#ifdef CUSTOM_ALLOCATOR
+    return alloc::CustomAllocator::GetAllocatedHeapSize(object);
+#else
     return mm::ObjectFactory<GCImpl>::GetAllocatedHeapSize(object);
+#endif
 }
 
 
 size_t gc::GC::GetHeapObjectsCountUnsafe() const noexcept {
+#ifndef CUSTOM_ALLOCATOR
     return impl_->objectFactory().GetObjectsCountUnsafe();
+#else
+    return 0;
+#endif
 }
 size_t gc::GC::GetTotalHeapObjectsSizeUnsafe() const noexcept {
+#ifndef CUSTOM_ALLOCATOR
     return impl_->objectFactory().GetTotalObjectsSizeUnsafe();
+#else
+    return 0;
+#endif
 }
 size_t gc::GC::GetExtraObjectsCountUnsafe() const noexcept {
+#ifndef CUSTOM_ALLOCATOR
     return mm::GlobalData::Instance().extraObjectDataFactory().GetSizeUnsafe();
+#else
+    return 0;
+#endif
 }
 size_t gc::GC::GetTotalExtraObjectsSizeUnsafe() const noexcept {
+#ifndef CUSTOM_ALLOCATOR
     return mm::GlobalData::Instance().extraObjectDataFactory().GetTotalObjectsSizeUnsafe();
+#else
+    return 0;
+#endif
 }
 
 size_t gc::GC::GetTotalHeapObjectsSizeBytes() const noexcept {
@@ -115,7 +135,9 @@ gc::GCSchedulerConfig& gc::GC::gcSchedulerConfig() noexcept {
 
 void gc::GC::ClearForTests() noexcept {
     impl_->gc().StopFinalizerThreadIfRunning();
+#ifndef CUSTOM_ALLOCATOR
     impl_->objectFactory().ClearForTests();
+#endif
     GCHandle::ClearForTests();
 }
 
diff --git a/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.hpp b/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.hpp
index 345dfd43a57..86499eaa0cc 100644
--- a/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.hpp
+++ b/kotlin-native/runtime/src/gc/cms/cpp/GCImpl.hpp
@@ -20,14 +20,22 @@ using GCImpl = ConcurrentMarkAndSweep;
 
 class GC::Impl : private Pinned {
 public:
+#ifdef CUSTOM_ALLOCATOR
+    Impl() noexcept : gc_(gcScheduler_) {}
+#else
     Impl() noexcept : gc_(objectFactory_, gcScheduler_) {}
+#endif
 
+#ifndef CUSTOM_ALLOCATOR
     mm::ObjectFactory<gc::GCImpl>& objectFactory() noexcept { return objectFactory_; }
+#endif
     GCScheduler& gcScheduler() noexcept { return gcScheduler_; }
     GCImpl& gc() noexcept { return gc_; }
 
 private:
+#ifndef CUSTOM_ALLOCATOR
     mm::ObjectFactory<gc::GCImpl> objectFactory_;
+#endif
     GCScheduler gcScheduler_;
     GCImpl gc_;
 };