diff --git a/milli/src/update/settings.rs b/milli/src/update/settings.rs
index c3e4ab3fa..af37a205c 100644
--- a/milli/src/update/settings.rs
+++ b/milli/src/update/settings.rs
@@ -1112,12 +1112,11 @@ impl InnerIndexSettingsDiff {
             || self.old.proximity_precision != self.new.proximity_precision
     }
 
-    /// Returns only the additional searchable fields if any
-    /// other searchable field has been modified, returns None.
+    /// Returns only the additional searchable fields.
+    /// If any other searchable field has been modified, returns None.
     pub fn only_additional_fields(&self) -> Option<HashSet<String>> {
         match (&self.old.user_defined_searchable_fields, &self.new.user_defined_searchable_fields) {
-            (None, None) | (Some(_), None) => None,
-            (None, Some(new)) => Some(new.iter().cloned().collect()),
+            (None, None) | (Some(_), None) | (None, Some(_)) => None, // None means *
             (Some(old), Some(new)) => {
                 let old: HashSet<_> = old.iter().cloned().collect();
                 let new: HashSet<_> = new.iter().cloned().collect();