diff --git a/poincare/src/great_common_divisor.cpp b/poincare/src/great_common_divisor.cpp
index ed53de17e..c3c7eaba4 100644
--- a/poincare/src/great_common_divisor.cpp
+++ b/poincare/src/great_common_divisor.cpp
@@ -69,7 +69,7 @@ Expression GreatCommonDivisor::shallowReduce(Context& context, Preferences::Angl
     }
   }
   if (c1.type() == ExpressionNode::Type::Rational) {
-    Rational r1 = static_cast<Rational>(c1);
+    Rational r1 = static_cast<Rational&>(c1);
     if (!r1.integerDenominator().isOne()) {
       return Undefined();
     }
@@ -77,8 +77,8 @@ Expression GreatCommonDivisor::shallowReduce(Context& context, Preferences::Angl
   if (c0.type() != ExpressionNode::Type::Rational || c1.type() != ExpressionNode::Type::Rational) {
     return *this;
   }
-  Rational r0 = static_cast<Rational>(c0);
-  Rational r1 = static_cast<Rational>(c1);
+  Rational r0 = static_cast<Rational&>(c0);
+  Rational r1 = static_cast<Rational&>(c1);
 
   Integer a = r0.signedIntegerNumerator();
   Integer b = r1.signedIntegerNumerator();