diff --git a/lib/global_id/global_id.rb b/lib/global_id/global_id.rb
index 71bd802..270a85a 100644
--- a/lib/global_id/global_id.rb
+++ b/lib/global_id/global_id.rb
@@ -51,7 +51,13 @@ def find(options = {})
   end
 
   def model_class
-    model_name.constantize
+    model = model_name.constantize
+
+    unless model <= GlobalID
+      model
+    else
+      raise ArgumentError, "GlobalID and SignedGlobalID cannot be used as model_class."
+    end
   end
 
   def ==(other)
diff --git a/test/cases/global_id_test.rb b/test/cases/global_id_test.rb
index 7f77304..22e55ce 100644
--- a/test/cases/global_id_test.rb
+++ b/test/cases/global_id_test.rb
@@ -177,6 +177,9 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_equal Person, @person_uuid_gid.model_class
     assert_equal Person::Child, @person_namespaced_gid.model_class
     assert_equal PersonModel, @person_model_gid.model_class
+    assert_raise ArgumentError do
+      person_gid = GlobalID.find 'gid://bcx/SignedGlobalID/5'
+    end
   end
 
   test ':app option' do