diff --git a/lib/activerecord-multi-tenant/model_extensions.rb b/lib/activerecord-multi-tenant/model_extensions.rb
index 0ec84f9..2056651 100644
--- a/lib/activerecord-multi-tenant/model_extensions.rb
+++ b/lib/activerecord-multi-tenant/model_extensions.rb
@@ -67,7 +67,7 @@ def inherited(subclass)
         partition_key = @partition_key
 
         # Create an implicit belongs_to association only if tenant class exists
-        if MultiTenant.tenant_klass_defined?(tenant_name)
+        if MultiTenant.tenant_klass_defined?(tenant_name, options)
           belongs_to tenant_name, **options.slice(:class_name, :inverse_of, :optional)
                                            .merge(foreign_key: options[:partition_key])
         end
@@ -103,7 +103,7 @@ def inherited(subclass)
             tenant_id
           end
 
-          if MultiTenant.tenant_klass_defined?(tenant_name)
+          if MultiTenant.tenant_klass_defined?(tenant_name, options)
             define_method "#{tenant_name}=" do |model|
               super(model)
               if send("#{partition_key}_changed?") && persisted? && !send("#{partition_key}_was").nil?
diff --git a/lib/activerecord-multi-tenant/multi_tenant.rb b/lib/activerecord-multi-tenant/multi_tenant.rb
index b2edb59..b541e33 100644
--- a/lib/activerecord-multi-tenant/multi_tenant.rb
+++ b/lib/activerecord-multi-tenant/multi_tenant.rb
@@ -5,8 +5,13 @@ class Current < ::ActiveSupport::CurrentAttributes
     attribute :tenant
   end
 
-  def self.tenant_klass_defined?(tenant_name)
-    !!tenant_name.to_s.classify.safe_constantize
+  def self.tenant_klass_defined?(tenant_name, options = {})
+    class_name = if options[:class_name].present?
+                   options[:class_name]
+                 else
+                   tenant_name.to_s.classify
+                 end
+    !!class_name.safe_constantize
   end
 
   def self.partition_key(tenant_name)
diff --git a/spec/activerecord-multi-tenant/multi_tenant_spec.rb b/spec/activerecord-multi-tenant/multi_tenant_spec.rb
index 0cae722..cedd0bb 100644
--- a/spec/activerecord-multi-tenant/multi_tenant_spec.rb
+++ b/spec/activerecord-multi-tenant/multi_tenant_spec.rb
@@ -64,4 +64,58 @@
       end
     end
   end
+
+  describe '.tenant_klass_defined?' do
+    context 'without options' do
+      before(:all) do
+        class SampleTenant < ActiveRecord::Base
+          multi_tenant :sample_tenant
+        end
+      end
+
+      it 'return true with valid tenant_name' do
+        expect(MultiTenant.tenant_klass_defined?(:sample_tenant)).to eq(true)
+      end
+
+      it 'return false with invalid_tenant_name' do
+        invalid_tenant_name = :tenant
+        expect(MultiTenant.tenant_klass_defined?(invalid_tenant_name)).to eq(false)
+      end
+    end
+
+    context 'with options' do
+      context 'and valid class_name' do
+        it 'return true' do
+          class SampleTenant < ActiveRecord::Base
+            multi_tenant :tenant
+          end
+
+          tenant_name = :tenant
+          options = {
+            class_name: 'SampleTenant'
+          }
+          expect(MultiTenant.tenant_klass_defined?(tenant_name, options)).to eq(true)
+        end
+
+        it 'return true when tenant class is nested' do
+          module SampleModule
+            class SampleNestedTenant < ActiveRecord::Base
+              multi_tenant :tenant
+            end
+            # rubocop:disable Layout/TrailingWhitespace
+            # Trailing whitespace is intentionally left here
+            
+            class AnotherTenant < ActiveRecord::Base
+            end
+            # rubocop:enable Layout/TrailingWhitespace
+          end
+          tenant_name = :tenant
+          options = {
+            class_name: 'SampleModule::SampleNestedTenant'
+          }
+          expect(MultiTenant.tenant_klass_defined?(tenant_name, options)).to eq(true)
+        end
+      end
+    end
+  end
 end