diff --git a/lib/active_storage_validations/content_type_validator.rb b/lib/active_storage_validations/content_type_validator.rb
index 95ed66b..77dcfe8 100644
--- a/lib/active_storage_validations/content_type_validator.rb
+++ b/lib/active_storage_validations/content_type_validator.rb
@@ -191,7 +191,7 @@ def invalid_content_type_option_message(content_type)
       if content_type.to_s.match?(/\//)
         <<~ERROR_MESSAGE
           You must pass valid content types to the validator
-          '#{content_type}' is not found in Marcel::TYPE_EXTS
+          '#{content_type}' is not found in Marcel content types (Marcel::TYPE_EXTS + Marcel::MAGIC)
         ERROR_MESSAGE
       else
         <<~ERROR_MESSAGE
@@ -215,7 +215,12 @@ def invalid_content_type?(content_type)
         raise ArgumentError, "'image/jpg' is not a valid content type, you should use 'image/jpeg' instead"
       end
 
-      Marcel::TYPE_EXTS[content_type.to_s] == nil
+      all_available_marcel_content_types.keys.exclude?(content_type.to_s)
+    end
+
+    def all_available_marcel_content_types
+      Marcel::MAGIC.map {|dd| dd.first }
+                   .each_with_object(Marcel::TYPE_EXTS) { |(k,v), h| h[k] = v unless h.key?(k) }
     end
 
     def invalid_extension?(content_type)
diff --git a/test/dummy/app/models/content_type/validator/check_validity_valid_content_type_ole_storage.rb b/test/dummy/app/models/content_type/validator/check_validity_valid_content_type_ole_storage.rb
new file mode 100644
index 0000000..cad0bea
--- /dev/null
+++ b/test/dummy/app/models/content_type/validator/check_validity_valid_content_type_ole_storage.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: content_type_validator_check_validity_valid_ct_ole_storages
+#
+#  id         :integer          not null, primary key
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+
+class ContentType::Validator::CheckValidityValidContentTypeOleStorage < ApplicationRecord
+  self.table_name = "content_type_validator_check_validity_valid_ct_ole_storages"
+
+  has_one_attached :valid
+  validates :valid, content_type: "application/x-ole-storage"
+end
+
diff --git a/test/dummy/db/schema.rb b/test/dummy/db/schema.rb
index 9096247..17c6790 100644
--- a/test/dummy/db/schema.rb
+++ b/test/dummy/db/schema.rb
@@ -115,7 +115,7 @@
     end
   end
 
-  %w(proc_option invalid_content_type_with invalid_content_type_in invalid_content_type_jpg invalid_extension regex_option).each do |invalid_case|
+  %w(proc_option invalid_content_type_with invalid_content_type_in invalid_content_type_jpg valid_ct_ole_storage invalid_extension regex_option).each do |invalid_case|
     create_table :"content_type_validator_check_validity_#{invalid_case.pluralize}", force: :cascade do |t|
       t.datetime :created_at, null: false
       t.datetime :updated_at, null: false
diff --git a/test/validators/content_type_validator_test.rb b/test/validators/content_type_validator_test.rb
index 4351c3a..45a57a0 100644
--- a/test/validators/content_type_validator_test.rb
+++ b/test/validators/content_type_validator_test.rb
@@ -49,15 +49,26 @@
           end
         end
 
-        describe "when the passed option is 'image/jpg'" do
-          subject { validator_test_class::CheckValidityInvalidContentTypeJpg.new(params) }
+        describe "Edge cases" do
+          describe "when the passed option is 'image/jpg'" do
+            subject { validator_test_class::CheckValidityInvalidContentTypeJpg.new(params) }
 
-          let(:error_message) do
-            "'image/jpg' is not a valid content type, you should use 'image/jpeg' instead"
+            let(:error_message) do
+              "'image/jpg' is not a valid content type, you should use 'image/jpeg' instead"
+            end
+
+            it 'raises an error at model initialization' do
+              error = assert_raises(ArgumentError) { subject }
+              assert_equal(error_message, error.message)
+            end
           end
 
-          it 'raises an error at model initialization' do
-            assert_raises(ArgumentError, error_message) { subject }
+          describe "when the passed option is in Marcel::MAGIC (e.g. 'application/x-ole-storage')" do
+            subject { validator_test_class::CheckValidityValidContentTypeOleStorage.new(params) }
+
+            it 'does not raise an error at model initialization' do
+              assert_nothing_raised { subject }
+            end
           end
         end
       end