diff --git a/src/common/serialization/vst3/plugin-factory.cpp b/src/common/serialization/vst3/plugin-factory.cpp
index b08abaad..cb1534fa 100644
--- a/src/common/serialization/vst3/plugin-factory.cpp
+++ b/src/common/serialization/vst3/plugin-factory.cpp
@@ -30,6 +30,7 @@ YaPluginFactory::YaPluginFactory(
         factory->getFactoryInfo(&info) == Steinberg::kResultOk) {
         factory_info = info;
     }
+    num_classes = factory->countClasses();
 
     auto factory2 = Steinberg::FUnknownPtr<Steinberg::IPluginFactory2>(factory);
     if (!factory2) {
@@ -89,8 +90,7 @@ YaPluginFactory::getFactoryInfo(Steinberg::PFactoryInfo* info) {
 }
 
 int32 PLUGIN_API YaPluginFactory::countClasses() {
-    // TODO: Implement
-    return 0;
+    return num_classes;
 }
 
 tresult PLUGIN_API
diff --git a/src/common/serialization/vst3/plugin-factory.h b/src/common/serialization/vst3/plugin-factory.h
index 74c8fec0..3a6ef4a5 100644
--- a/src/common/serialization/vst3/plugin-factory.h
+++ b/src/common/serialization/vst3/plugin-factory.h
@@ -88,6 +88,8 @@ class YaPluginFactory : public Steinberg::IPluginFactory3 {
 
     // For `IPluginFactory::getFactoryInfo`
     std::optional<Steinberg::PFactoryInfo> factory_info;
+    // For `IPluginFactory::countClasses`
+    int num_classes;
 
     template <typename S>
     void serialize(S& s) {
@@ -97,6 +99,7 @@ class YaPluginFactory : public Steinberg::IPluginFactory3 {
               });
         s.ext(factory_info, bitsery::ext::StdOptional{},
               [](S& s, Steinberg::PFactoryInfo& info) { s.object(info); });
+        s.value4b(num_classes);
     }
 };