diff --git a/poincare/include/poincare/number.h b/poincare/include/poincare/number.h
index cf72e2566..71c98b11a 100644
--- a/poincare/include/poincare/number.h
+++ b/poincare/include/poincare/number.h
@@ -44,7 +44,7 @@ public:
   static Number Power(const Number & i, const Number & j);
   static int NaturalOrder(const Number & i, const Number & j);
 
-  Number setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit) const { return static_cast<Number>(Expression::setSign(s, context, angleUnit)); }
+  Number setSign(ExpressionNode::Sign s, Context & context, Preferences::AngleUnit angleUnit) { return static_cast<Number>(Expression::setSign(s, context, angleUnit)); }
 protected:
   Number() : Expression() {}
   NumberNode * node() const { return static_cast<NumberNode *>(Expression::node()); }