diff --git a/mailsystem.install b/mailsystem.install
index c7591d1..918e5eb 100644
--- a/mailsystem.install
+++ b/mailsystem.install
@@ -94,6 +94,10 @@ function mailsystem_update_7300() {
   }
   mailsystem_set($mail_system);
 
+  if (empty($genclasses)) {
+    return t('No dynamically generated classes to convert.');
+  }
+
   // Remove the generated classes from the registry.
   db_delete('registry')
     ->condition('name', array_keys($genclasses))