diff --git a/apps/sequence/sequence.cpp b/apps/sequence/sequence.cpp
index 1a45135de..11f9be50a 100644
--- a/apps/sequence/sequence.cpp
+++ b/apps/sequence/sequence.cpp
@@ -104,14 +104,14 @@ void Sequence::setType(Type type) {
   m_indexBuffer[1] = -1;
 }
 
-Poincare::Expression * Sequence::firstInitialConditionExpression() {
+Poincare::Expression * Sequence::firstInitialConditionExpression() const {
   if (m_firstInitialConditionExpression == nullptr) {
     m_firstInitialConditionExpression = Poincare::Expression::parse(m_firstInitialConditionText);
   }
   return m_firstInitialConditionExpression;
 }
 
-Poincare::Expression * Sequence::secondInitialConditionExpression() {
+Poincare::Expression * Sequence::secondInitialConditionExpression() const {
   if (m_secondInitialConditionExpression == nullptr) {
     m_secondInitialConditionExpression = Poincare::Expression::parse(m_secondInitialConditionText);
   }
@@ -255,13 +255,13 @@ float Sequence::evaluateAtAbscissa(float x, Poincare::Context * context) const {
       }
       if (n == 0) {
         m_indexBuffer[0] = 0;
-        m_buffer[0] = m_firstInitialConditionExpression->approximate(*context);
+        m_buffer[0] = firstInitialConditionExpression()->approximate(*context);
         return m_buffer[0];
       }
       LocalContext subContext = LocalContext(context);
       Poincare::Symbol nSymbol = Poincare::Symbol(symbol());
       int start = m_indexBuffer[0] < 0 || m_indexBuffer[0] > n ? 0 : m_indexBuffer[0];
-      float un = m_indexBuffer[0] < 0 || m_indexBuffer[0] > n ? m_firstInitialConditionExpression->approximate(*context) : m_buffer[0];
+      float un = m_indexBuffer[0] < 0 || m_indexBuffer[0] > n ? firstInitialConditionExpression()->approximate(*context) : m_buffer[0];
       for (int i = start; i < n; i++) {
         subContext.setValueForSequenceRank(un, name(), 0);
         Poincare::Complex e = Poincare::Complex::Float(i);
@@ -278,20 +278,20 @@ float Sequence::evaluateAtAbscissa(float x, Poincare::Context * context) const {
         return NAN;
       }
       if (n == 0) {
-        return m_firstInitialConditionExpression->approximate(*context);
+        return firstInitialConditionExpression()->approximate(*context);
       }
       if (n == 1) {
         m_indexBuffer[0] = 0;
-        m_buffer[0] = m_firstInitialConditionExpression->approximate(*context);
+        m_buffer[0] = firstInitialConditionExpression()->approximate(*context);
         m_indexBuffer[1] = 1;
-        m_buffer[1] = m_secondInitialConditionExpression->approximate(*context);
+        m_buffer[1] = secondInitialConditionExpression()->approximate(*context);
         return m_buffer[1];
       }
       LocalContext subContext = LocalContext(context);
       Poincare::Symbol nSymbol = Poincare::Symbol(symbol());
       int start = m_indexBuffer[0] >= 0 && m_indexBuffer[0] < n && m_indexBuffer[1] > 0 && m_indexBuffer[1] <= n && m_indexBuffer[0] + 1 == m_indexBuffer[1] ? m_indexBuffer[0] : 0;
-      float un = m_indexBuffer[0] >= 0 && m_indexBuffer[0] < n && m_indexBuffer[1] > 0 && m_indexBuffer[1] <= n && m_indexBuffer[0] + 1 == m_indexBuffer[1] ? m_buffer[0] : m_firstInitialConditionExpression->approximate(*context);
-      float un1 =  m_indexBuffer[0] >= 0 && m_indexBuffer[0] < n && m_indexBuffer[1] > 0 && m_indexBuffer[1] <= n && m_indexBuffer[0] + 1 == m_indexBuffer[1] ? m_buffer[1] : m_secondInitialConditionExpression->approximate(*context);
+      float un = m_indexBuffer[0] >= 0 && m_indexBuffer[0] < n && m_indexBuffer[1] > 0 && m_indexBuffer[1] <= n && m_indexBuffer[0] + 1 == m_indexBuffer[1] ? m_buffer[0] : firstInitialConditionExpression()->approximate(*context);
+      float un1 =  m_indexBuffer[0] >= 0 && m_indexBuffer[0] < n && m_indexBuffer[1] > 0 && m_indexBuffer[1] <= n && m_indexBuffer[0] + 1 == m_indexBuffer[1] ? m_buffer[1] : secondInitialConditionExpression()->approximate(*context);
       for (int i = start; i < n-1; i++) {
         subContext.setValueForSequenceRank(un, name(), 0);
         subContext.setValueForSequenceRank(un1, name(), 1);
diff --git a/apps/sequence/sequence.h b/apps/sequence/sequence.h
index 73a9f0991..09563df98 100644
--- a/apps/sequence/sequence.h
+++ b/apps/sequence/sequence.h
@@ -22,8 +22,8 @@ public:
   void setType(Type type);
   const char * firstInitialConditionText();
   const char * secondInitialConditionText();
-  Poincare::Expression * firstInitialConditionExpression();
-  Poincare::Expression * secondInitialConditionExpression();
+  Poincare::Expression * firstInitialConditionExpression() const;
+  Poincare::Expression * secondInitialConditionExpression() const;
   Poincare::ExpressionLayout * firstInitialConditionLayout();
   Poincare::ExpressionLayout * secondInitialConditionLayout();
   void setContent(const char * c) override;
@@ -46,8 +46,8 @@ private:
   Type m_type;
   char m_firstInitialConditionText[TextField::maxBufferSize()];
   char m_secondInitialConditionText[TextField::maxBufferSize()];
-  Poincare::Expression * m_firstInitialConditionExpression;
-  Poincare::Expression * m_secondInitialConditionExpression;
+  mutable Poincare::Expression * m_firstInitialConditionExpression;
+  mutable Poincare::Expression * m_secondInitialConditionExpression;
   Poincare::ExpressionLayout * m_firstInitialConditionLayout;
   Poincare::ExpressionLayout * m_secondInitialConditionLayout;
   Poincare::ExpressionLayout * m_nameLayout;
diff --git a/apps/shared/function.cpp b/apps/shared/function.cpp
index 7cb2bb0fa..354ba28f9 100644
--- a/apps/shared/function.cpp
+++ b/apps/shared/function.cpp
@@ -60,7 +60,7 @@ const char * Function::name() const {
   return m_name;
 }
 
-Poincare::Expression * Function::expression() {
+Poincare::Expression * Function::expression() const {
   if (m_expression == nullptr) {
     m_expression = Expression::parse(m_text);
   }
@@ -95,7 +95,7 @@ float Function::evaluateAtAbscissa(float x, Poincare::Context * context) const {
   Poincare::Symbol xSymbol = Poincare::Symbol(symbol());
   Poincare::Complex e = Poincare::Complex::Float(x);
   variableContext.setExpressionForSymbolName(&e, &xSymbol);
-  return m_expression->approximate(variableContext);
+  return expression()->approximate(variableContext);
 }
 
 void Function::tidy() {
diff --git a/apps/shared/function.h b/apps/shared/function.h
index b3e0b05a5..cdf64bc4c 100644
--- a/apps/shared/function.h
+++ b/apps/shared/function.h
@@ -18,7 +18,7 @@ public:
   const char * text() const;
   const char * name() const;
   KDColor color() const { return m_color; }
-  Poincare::Expression * expression();
+  Poincare::Expression * expression() const;
   Poincare::ExpressionLayout * layout();
   virtual bool isDefined();
   bool isActive();
@@ -29,7 +29,7 @@ public:
   virtual float evaluateAtAbscissa(float x, Poincare::Context * context) const;
   virtual void tidy();
 protected:
-  Poincare::Expression * m_expression;
+  mutable Poincare::Expression * m_expression;
 private:
   virtual char symbol() const = 0;
   char m_text[TextField::maxBufferSize()];