diff --git a/apps/shared/cartesian_function.cpp b/apps/shared/cartesian_function.cpp
index 1196cdf29..70ec010d5 100644
--- a/apps/shared/cartesian_function.cpp
+++ b/apps/shared/cartesian_function.cpp
@@ -95,15 +95,7 @@ Poincare::Expression CartesianFunction::expressionReduced(Poincare::Context * co
 }
 
 I18n::Message CartesianFunction::parameterMessageName() const {
-  PlotType type = plotType();
-  if (type == PlotType::Cartesian) {
-    return I18n::Message::X;
-  }
-  if (type == PlotType::Polar) {
-    return I18n::Message::Theta;
-  }
-  assert(plotType() == PlotType::Parametric);
-  return I18n::Message::T;
+  return ParameterMessageForPlotType(plotType());
 }
 
 CodePoint CartesianFunction::symbol() const {
@@ -161,6 +153,17 @@ void CartesianFunction::setPlotType(PlotType newPlotType) {
   }
 }
 
+I18n::Message CartesianFunction::ParameterMessageForPlotType(PlotType plotType) {
+  if (plotType == PlotType::Cartesian) {
+    return I18n::Message::X;
+  }
+  if (plotType == PlotType::Polar) {
+    return I18n::Message::Theta;
+  }
+  assert(plotType == PlotType::Parametric);
+  return I18n::Message::T;
+}
+
 template <typename T>
 Poincare::Coordinate2D<T> CartesianFunction::privateEvaluateXYAtParameter(T t, Poincare::Context * context) const {
   Coordinate2D<T> x1x2 = templatedApproximateAtParameter(t, context);
diff --git a/apps/shared/cartesian_function.h b/apps/shared/cartesian_function.h
index 786b1c9fc..d0b9e5b8a 100644
--- a/apps/shared/cartesian_function.h
+++ b/apps/shared/cartesian_function.h
@@ -27,6 +27,7 @@ public:
   };
   PlotType plotType() const;
   void setPlotType(PlotType plotType);
+  static I18n::Message ParameterMessageForPlotType(PlotType plotType);
 
   // Evaluation
   Poincare::Coordinate2D<double> evaluate2DAtParameter(double t, Poincare::Context * context) const {