diff --git a/apps/calculation/app.cpp b/apps/calculation/app.cpp
index c6ec10f9b..2a947cf8c 100644
--- a/apps/calculation/app.cpp
+++ b/apps/calculation/app.cpp
@@ -77,4 +77,8 @@ bool App::textFieldDidReceiveEvent(::TextField * textField, Ion::Events::Event e
   return false;
 }
 
+const char * App::XNT() {
+  return "x";
+}
+
 }
diff --git a/apps/calculation/app.h b/apps/calculation/app.h
index 922772f69..a9b616599 100644
--- a/apps/calculation/app.h
+++ b/apps/calculation/app.h
@@ -30,6 +30,7 @@ public:
   };
   Poincare::Context * localContext() override;
   bool textFieldDidReceiveEvent(::TextField * textField, Ion::Events::Event event) override;
+  const char * XNT() override;
 private:
   App(Container * container, Snapshot * snapshot);
   LocalContext m_localContext;