diff --git a/app/lib/omni_auth/strategies/azure_ad_auth.rb b/app/lib/omni_auth/strategies/azure_ad_auth.rb
index 86094ee86..34695e271 100644
--- a/app/lib/omni_auth/strategies/azure_ad_auth.rb
+++ b/app/lib/omni_auth/strategies/azure_ad_auth.rb
@@ -53,7 +53,7 @@ def user_roles
       # query parameters. Azure fails validation because that doesn't match the
       # registered callback.
       def callback_url
-        options[:redirect_uri]
+        options[:redirect_uri] || (full_host + script_name + callback_path)
       end
     end
   end