diff --git a/addons/mail/static/src/components/chat_window/chat_window.js b/addons/mail/static/src/components/chat_window/chat_window.js
index 47a06c073b8..69d08228416 100644
--- a/addons/mail/static/src/components/chat_window/chat_window.js
+++ b/addons/mail/static/src/components/chat_window/chat_window.js
@@ -38,16 +38,6 @@ export class ChatWindow extends Component {
         return this.messaging && this.messaging.models['ChatWindow'].get(this.props.localId);
     }
 
-    /**
-     * Get the content of placeholder for the autocomplete input of
-     * 'new_message' chat window.
-     *
-     * @returns {string}
-     */
-    get newMessageFormInputPlaceholder() {
-        return this.env._t("Search user...");
-    }
-
     //--------------------------------------------------------------------------
     // Private
     //--------------------------------------------------------------------------
diff --git a/addons/mail/static/src/components/chat_window/chat_window.xml b/addons/mail/static/src/components/chat_window/chat_window.xml
index 918ac114657..7631313cc07 100644
--- a/addons/mail/static/src/components/chat_window/chat_window.xml
+++ b/addons/mail/static/src/components/chat_window/chat_window.xml
@@ -41,7 +41,7 @@
                         </span>
                         <AutocompleteInput
                             className="'o_ChatWindow_newMessageFormInput'"
-                            placeholder="newMessageFormInputPlaceholder"
+                            placeholder="chatWindow.newMessageFormInputPlaceholder"
                             select="_onAutocompleteSelect"
                             source="_onAutocompleteSource"
                             onFocusin="chatWindow.onFocusInNewMessageFormInput"
diff --git a/addons/mail/static/src/models/chat_window/chat_window.js b/addons/mail/static/src/models/chat_window/chat_window.js
index 259449dbeff..94fb8e794a6 100644
--- a/addons/mail/static/src/models/chat_window/chat_window.js
+++ b/addons/mail/static/src/models/chat_window/chat_window.js
@@ -286,6 +286,13 @@ registerModel({
             }
             return this.env._t("New message");
         },
+        /**
+         * @private
+         * @returns {string}
+         */
+        _computeNewMessageFormInputPlaceholder() {
+            return this.env._t("Search user...");
+        },
         /**
          * @private
          * @returns {ThreadViewer}
@@ -462,6 +469,13 @@ registerModel({
         name: attr({
             compute: '_computeName',
         }),
+        /**
+         * The content of placeholder for the autocomplete input of
+         * 'new_message' chat window.
+         */
+        newMessageFormInputPlaceholder: attr({
+            compute: '_computeNewMessageFormInputPlaceholder',
+        }),
         /**
          * Determines the `Thread` that should be displayed by `this`.
          * If no `Thread` is linked, `this` is considered "new message".