diff --git a/src/config.rs b/src/config.rs
index b56957f..e208b9f 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -149,6 +149,20 @@ impl Config {
         config.state_config.strings.message_from =
             config.state_config.strings.message_from.trim().to_string() + " ";
 
+        // Add the optional word to fields without a required_feedback.
+        config
+            .state_config
+            .custom_fields
+            .iter_mut()
+            .filter(|field| field.required_feedback.is_none())
+            .for_each(|field| {
+                field.label = format!(
+                    "{} ({})",
+                    field.label.trim(),
+                    config.state_config.strings.optional
+                );
+            });
+
         Ok(config)
     }
 }